Poland said Tuesday that Russia is shifting some short-range nuclear weapons to Belarus, a move Polish President Andrzej Duda said could change the NATO alliance in the region. 

Both Russian President Vladimir Putin and his Belarusian counterpart, Alexander Lukashenko, said last month Moscow had already shipped some of its tactical nuclear weapons to Belarus after announcing the plan in March. 

News of the move came a day after the U.S. Embassy in Belarus issued an alert Monday for all American citizens in the country to leave immediately and warned against traveling there.

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The warning comes after Lithuania closed two of its major border crossings with Belarus over concerns about the Russian mercenary group Wagner that has established operations in the country. 

Moscow said it would maintain control over the warheads it sends to Belarus. Belarus is a critical and strategically important nation, as it borders NATO such as Poland, Lithuania and Latvia in addition to Ukraine. 

Duda made his comments at a joint news conference with visiting Portuguese President Marcelo Rebelo de Sousa.

"I was telling President (de Sousa) about the implementation of the declarations by Vladimir Putin that Russia’s tactical nuclear weapons will be moved to the territory of Belarus," he said. "Indeed, this process is taking place, we are seeing that."

As Russia's war in Ukraine continues, Ukrainians are reportedly ramping up arms production. Meanwhile, Ukraine continues to receive millions in military aid from NATO countries.

Fox News Digital's Bradford Betz contributed to this report. 

Canada will challenge what Ottawa described as "unfair, unjust and illegal" U.S. duties on Canadian softwood lumber products, the trade ministry said on Tuesday.

The softwood lumber tariffs are the legacy of a decades-long trade dispute over the structure of Canada's timber sector that could not be resolved when a quota agreement expired in 2015.

U.S. producers say the Canadian exports are unfairly subsidized and in July, the country's commerce department ruled that most Canadian softwood lumber would be subject to a 7.99% tax.

Canada on Monday filed notices of intent to commence judicial review regarding those duties, the trade ministry said in a statement, adding that Ottawa remained willing to discuss a negotiated outcome with Washington.

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"For years, the United States has imposed unfair, unjust and illegal duties on Canadian softwood lumber, hurting Canadian industry and increasing housing costs in both countries," Trade Minister Mary Ng said in the statement.

"Canada is taking the necessary steps to actively defend the interests of our softwood lumber industry and the workers and communities that rely on it."

The United States has said that Canadian timber harvested from federal and provincial lands with low government-set stumpage fees constitutes an unfair subsidy, while most U.S. timber is harvested from private land at market rates.

The U.S. Commerce Department did not immediately respond to a request for comment.