President Biden has not been seen publicly since a letter was released announcing that he would no longer seek re-election and is endorsing Vice President Harris to replace him as the Democrats' nominee. 

In a letter released on X Sunday, Biden said he believes it is in the "best interest of my party and the country for me to stand down and focus solely on fulfilling my duties as President for the remainder of my term," adding, "I will speak to the Nation later this week in more detail about by decision." 

According to the president's public schedule, Biden was at his house in Rehoboth Beach, Delaware, at the time the letter was sent out on social media, though he had no public appearances scheduled that day. The same goes for Monday, when his public schedule shows Biden at 10 a.m. ET will receive his daily briefing, which is closed to the press, with no public events currently scheduled.

The White House has yet to release additional details about Biden's schedule for the rest of the week.

HOW DOES KAMALA HARRIS POLL AGAINST DONALD TRUMP?

Last week, Biden began to self-isolate after reportedly testing positive for COVID-19. 

In a letter updating the status of 81-year-old Biden's medical condition on Friday, the physician to the president, Dr. Kevin O'Connor, wrote that Biden "completed his sixth dose of PAXLOVID this morning."

Biden "is still experiencing a loose, non-productive cough and hoarseness, but his symptoms continue to improve steadily," O'Connor wrote in the letter released by the White House. 

HARRIS OUTPERFORMS BIDEN IN 2024 SHOWDOWN WITH TRUMP: POLL

"His pulse, blood pressure, respiratory rate and temperature remain absolutely normal," the doctor said. "His oxygen saturation continues to be excellent on room air. His lungs remain clear." 

The doctor said Biden has the KP .2.3 variant, which accounts for approximately 33.3% of new infections in the United States, according to the U.S. Centers for Disease Control and Prevention. 

"The President continues to tolerate treatment well and will continue PAXLOVID as planned," the letter says. "He continues to perform all his presidential duties." 

A person familiar with Biden's schedule confirmed to the AP on Sunday that Biden will host Israeli Prime Minister Benjamin Netanyahu at the White House this week. The official, speaking on condition of anonymity because they were not authorized to comment publicly, said the exact timing of the meeting has not been established because Biden is recovering from COVID-19.

Netanyahu on Monday left for Washington, D.C., where he is expected to deliver a speech before the Congress at a time of great uncertainty following Biden’s withdrawal from the presidential race. The prime minister is scheduled to address Congress on Wednesday. He is also expected to meet with Harris.

CLICK TO GET THE FOX NEWS APP

Before stepping on the plane, Netanyahu said he would emphasize the theme of Israel's bipartisanship in his speech and said Israel would remain America's key ally in the Middle East "regardless who the American people choose as their next president," The Associated Press reported. 

"In this time of war and uncertainty, it's important that Israel's enemies know that America and Israel stand together," he said.

The Associated Press contributed to this report. 

Vice President Harris’ presidential campaign has raised nearly $50 million in grassroots donations since President Biden suspended his re-election bid and endorsed her, Fox News Digital has learned. 

"Since the President endorsed Vice President Harris yesterday afternoon, everyday Americans have given $49.6 million in grassroots donations to her campaign," the Harris campaign told Fox News Digital. 

BIDEN ENDS BID FOR SECOND TERM IN WHITE HOUSE AS HE DROPS OUT OF HIS 2024 REMATCH WITH TRUMP

The campaign told Fox News Digital that the figure represents grassroots donations raised across "all entities, including ActBlue." 

Harris announced her presidential campaign Sunday afternoon just after Biden announced he would drop out of the 2024 race, amid pressure from within the Democratic Party. 

The unprecedented announcement came as an increasing number of Democrat lawmakers had begun to publicly call for Biden to step aside and the party's leadership reportedly was engaged in efforts to convince Biden, 81, he could not win in November's general election against former President Trump, the 2024 GOP nominee who Biden defeated four years ago to win the White House.

Biden quickly offered his "full support and endorsement" for Harris to take over as the party's presidential nominee.

"It has been the greatest honor of my life to serve as your president," Biden wrote in a public letter. "While it has been my intention to seek reelection, I believe it is in the best interests of my party and the country for me to stand down and focus solely on fulfilling my duties as president for the remainder of my term."

Biden said he will formally address the nation later this week about his decision. 

In a social media post, Biden backed Harris to take over as the party's standard-bearer.

"My very first decision as the party nominee in 2020 was to pick Kamala Harris as my Vice President. And it’s been the best decision I’ve made. Today I want to offer my full support and endorsement for Kamala to be the nominee of our party this year. Democrats — it’s time to come together and beat Trump. Let’s do this," Biden wrote.

TRUMP SAYS BIDEN 'IS NOT FIT TO SERVE': 'WHO IS GOING TO BE RUNNING THE COUNTRY FOR THE NEXT 5 MONTHS?'

The president's endorsement could dissuade any serious completion from other Democrats who may have mulled a bid for the presidential nomination and could clear a path for the vice president to succeed Biden as the party's nominee.

Harris has already gained endorsements from more than half a dozen governors, including California Gov. Gavin Newsom and New York Gov. Kathy Hochul; along with more than 178 Democratic lawmakers in the House and Senate. 

Harris, in a statement about two hours after Biden's announcement, said she is "honored to have the President’s endorsement and my intention is to earn and win this nomination."

"Over the past year, I have traveled across the country, talking with Americans about the clear choice in this momentous election. And that is what I will continue to do in the days and weeks ahead," she added. "I will do everything in my power to unite the Democratic Party—and unite our nation—to defeat Donald Trump and his extreme Project 2025 agenda."

The vice president praised her boss, thanking Biden "for his extraordinary leadership as President of the United States and for his decades of service to our country. His remarkable legacy of accomplishment is unmatched in modern American history, surpassing the legacy of many Presidents who have served two terms in office."

A source familiar told Fox News that Biden and Harris spoke multiple times on Sunday ahead of the president's stunning announcement.

Biden's endorsement of Harris was quickly followed by two top party elders, former President Bill Clinton and former Secretary of State and former Sen. Hillary Clinton, the 2016 Democratic presidential nominee.

"We are honored to join the President in endorsing Vice President Harris and will do whatever we can to support her."

LinkedIn co-founder Reid Hoffman, one of the Biden campaign’s biggest donors, also quickly endorsed Harris.

Former President Obama, however, has not yet endorsed her, and is instead backing a process where an "outstanding" nominee can emerge. 

"We will be navigating uncharted waters in the days ahead. But I have extraordinary confidence that the leaders of our party will be able to create a process from which an outstanding nominee emerges," the former president wrote in a letter.

Obama and former first lady Michelle Obama were among the scores of top Democrats praising Biden for putting the nation and the party over personal ambitions.

"Joe Biden has been one of America’s most consequential presidents, as well as a dear friend and partner to me. Today, we’ve also been reminded — again — that he’s a patriot of the highest order." the Obamas wrote.

Former House Speaker Nancy Pelosi, House Democratic Leader Hakeem Jeffries, and Senate Majority Leader Chuck Schumer have not yet endorsed Harris. 

Fox News' Paul Steinhauser contributed to this report.