Absences among transportation security workers this weekend reached their highest since a partial government shutdown began five weeks ago, the Department of Homeland Security said on Sunday, as immigration enforcement agents prepared to fill in for them at some of the busiest U.S. airports.

Nationwide, about 11.5% of Transportation Security Administration staff were absent on Saturday, DHS said, but that figure soared to 42.4% at George Bush Intercontinental Airport in Houston, 33.4% at John F. Kennedy International Airport in New York and 33.6% at Hartsfield-Jackson Atlanta International Airport.

Overall, more than 9% of TSA employees have been absent from work over the past seven days, leading to lengthy lines for passengers trying to get to their gates, according to DHS.

To help fill the staffing gaps, hundreds of Immigration and Customs Enforcement agents will deploy to airports starting on Monday, officials have said.

DHS said on Sunday it would not publicly share details about the ICE deployment, in order to preserve operational security. Sources briefed on the matter said the current plan calls for deploying ICE agents to 14 locations, although that figure may change.

Tens of thousands of airport security personnel have been working without pay for weeks while congressional Democrats and Republicans argue over a budget for DHS.

“Many TSA officers cannot pay their rent, buy food, or afford to put gas in their cars — forcing them to call out sick from work,” a DHS spokesperson said on Sunday.

Trump announced on Saturday that ICE agents would be sent to airports unless Democratic lawmakers agree to fund DHS. Democrats have criticized the department’s immigration operations and are demanding a change in rules.

For now, ICE agents will not be deployed in areas behind security checkpoints because they lack the specific clearance needed, the sources said.

Border czar Tom Homan said on Sunday that sending out immigration agents to bolster short-staffed TSA teams will speed up airport lines, but the union for TSA workers said that does not solve what they see as the underlying problem of pay.

In appearances on Sunday news shows, Homan and Transportation Secretary Sean Duffy argued that ICE personnel can help with airport security screening, starting on Monday, even though they have not been specifically trained for it.

“When we deploy tomorrow, we’ll have a well thought-out plan to execute,” Homan said on CNN’s “State of the Union” program.

Hundreds of TSA agents have simply resigned, according to their labor union and TSA.

“ICE will do the job far better than ever done before!” Trump wrote in a Sunday morning social media post.

Details of how ICE agents would help with the lines were scant, although Homan told CNN a plan would be in place by the end of the day “to move those lines along.”

Homan and Duffy, in separate interviews, had different ideas about how the ICE agents might be deployed. Homan said he doubted ICE agents would operate X-ray baggage and passenger screening machines because they did not have experience. Duffy, in contrast, said ICE agents “know how to pat people down, they know how to run the X-ray machines.”

The labor union representing TSA workers criticized Trump’s decision, saying their members spend months in training learning to detect explosives and weapons.

“Our members at TSA have been showing up every day, without a paycheck, because they believe in the mission of keeping the flying public safe,” Everett Kelley, National President of the American Federation of Government Employees, said in a statement. “They deserve to be paid, not replaced by untrained, armed agents who have shown how dangerous they can be.”

Unlike TSA employees, ICE agents have continued to get paid by the government through a separate funding provision while lawmakers debate whether ICE funding should be tied to new rules and procedures.

Democrats have said new rules are needed after masked ICE agents fatally shot two U.S. citizens in the streets of Minneapolis earlier this year. The two had come out to protest or observe Trump’s deportation surge in Minnesota.

Hakeem Jeffries, a New York Democrat and the minority leader in the U.S. House of Representatives, told CNN that his caucus is open to a separate funding agreement for TSA employees while lawmakers debate measures to “get ICE under control.” But there has been little movement on an actual deal so far, especially in the Senate.

“We have an obligation to not fund an agency that is acting this lawlessly,” Senator Chris Murphy, a Connecticut Democrat, told NBC’s “Meet the Press” program.

(Reporting by Jonathan Allen in New York, David Shepardson in Washington and Rishabh Jaiswal in Bengaluru; Additional writing by Kristina Cooke in San Francisco; Editing by Elaine Hardcastle, Aurora Ellis, Sergio Non and Edmund Klamann)

Iran said on Sunday it would strike the energy and water systems of its Gulf neighbours in retaliation if U.S. President Donald Trump follows through with a threat to hit Iran’s electricity grid in 48 hours, escalating the three-week-old war.

The prospect of tit-for-tat strikes on civilian infrastructure could deepen the regional crisis and further rattle global markets when they reopen on Monday morning.

Air raid sirens sounded across Israel from the early hours of Sunday, warning of incoming missiles from Iran, after scores of people were hurt overnight in two separate attacks in the southern Israeli towns of Arad and Dimona.

The Israeli military said hours later that it was striking Tehran in response.

Trump threatened overnight to “obliterate” Iran’s power plants if Tehran did not fully reopen the Strait of Hormuz within 48 hours, barely a day after he talked about “winding down” the war. He made the new threat as U.S. Marines and heavy landing craft are heading to the region.

But while attacks on electricity could hurt Iran, they would be potentially catastrophic for its Gulf neighbors, which consume around five times as much power per capita. Electricity makes their gleaming desert cities habitable, and most of them produce nearly all of their drinking water by purifying it from the sea.

Iran’s Parliament Speaker Mohammad Baqer Qalibaf wrote on X that critical infrastructure and energy facilities in the Middle East could be “irreversibly destroyed” should Iranian power plants be attacked.

Iran’s Revolutionary Guards said it would also mean the shipping lane where a fifth of global oil and liquefied natural gas normally transits along Iran’s southern coast would remain shut.

“The Strait of Hormuz will be completely closed and will not be opened until our destroyed power plants are rebuilt,” the Guards said in a statement.

More than 2,000 people have been killed during the war the U.S. and Israel launched on February 28, which has upended markets, spiked fuel costs, fuelled global inflation fears and convulsed the postwar Western alliance.

“President Trump’s threat has now placed a 48-hour ticking time bomb of elevated uncertainty over markets,” said IG market analyst Tony Sycamore, who expects stock markets to fall when they reopen on Monday.

Oil prices jumped on Friday, ending the day at their highest in nearly four years.

Markets already under severe strain from blockaded shipping were further rattled last week when Israel attacked a major gas field in Iran, and Tehran responded with strikes on neighbors Saudi Arabia, Qatar and Kuwait, raising the prospect of damage hindering energy output even if tankers resume sailing.

Iranian attacks have effectively closed the Strait of Hormuz, causing the worst oil crisis since the 1970s. Its near-closure sent European gas prices surging as much as 35% last week.

“If Iran doesn’t FULLY OPEN, WITHOUT THREAT, the Strait of Hormuz, within 48 HOURS from this exact point in time, the United States of America will hit and obliterate their various POWER PLANTS, STARTING WITH THE BIGGEST ONE FIRST!” Trump posted on social media around 7:45 p.m. EDT (2345 GMT) on Saturday.

Iranian media quoted the country’s representative to the International Maritime Organisation as saying the strait remains open to all shipping except vessels linked to “Iran’s enemies.”

Ali Mousavi said passage through the waterway was possible by coordinating security and safety arrangements with Tehran.

Ship-tracking data shows some vessels, such as Indian-flagged ships and a Pakistani oil tanker, have negotiated safe passage through the strait. But the vast majority of ships have remained holed up inside.

Iran’s Khatam al-Anbiya military command headquarters said on Sunday if the U.S. hit Iran’s fuel and energy infrastructure, Iran would attack all U.S. energy, information technology and desalination infrastructure in the region.

Striking major Iranian power plants could trigger blackouts, crippling everything from pumps and refineries to export terminals and military command centers.

The United States and Israel say they have seriously degraded Iran’s ability to project force beyond its borders with their three weeks of intensive air strikes.

But Tehran fired its first known long-range ballistic missiles with a range of 4,000 km (2,500 miles) on Friday towards a U.S.-British Indian Ocean ‌military base, expanding the risk of attacks beyond the Middle East.

An Iranian strike also landed near Israel’s secretive nuclear reactor about 13 km (8 miles) southeast of the city of Dimona.

The war has been taking place alongside a confrontation on a separate front between Israel and Lebanon’s Hezbollah, backed by Iran, with Israel saying on Sunday its troops had raided a number of the armed group’s sites in southern Lebanon.

Hezbollah said it had attacked several border areas in northern Israel. Israeli emergency services said one person was killed in a kibbutz near the border. Israel later said it was checking whether the death was caused by Israeli fire.

Hezbollah has fired hundreds of rockets at Israel since it entered the regional war on March 2, prompting an Israeli offensive that has killed more than 1,000 people in Lebanon.

Israel said it had instructed the military to accelerate the demolition of Lebanese homes in “frontline villages” to end threats to Israelis, and to destroy all bridges over Lebanon’s Litani River which it said were used for “terrorist activity.”

Pope Leo appealed for an end to the conflict. “The death and suffering caused by this war are a scandal to the whole human family,” he said.

(Reporting by Phil Stewart and Idrees Ali in Washington, Andrew Mills in Doha, Timour Azhari in Riyadh, Maayan Lubell in Jerusalem and Alexander Cornwell in Tel Aviv; Additional reporting by Reuters bureaus; Writing by Lisa Shumaker, Michael Perry, William Maclean; Editing by Alexander Smith, Peter Graff and Jon Boyle)