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President Biden made another sudden change to travel plans, canceling a trip to Delaware and opting to stay in Washington D.C. over the weekend as he had initially planned.

Biden was set to travel to Delaware Sunday to tend to a family-related issue, despite initially planning to stay in Washington D.C. over the weekend as the crisis between Ukraine and Russia escalated. The evolving plans come after a meeting with national security aides on Sunday, while the president spoke with French President Emmanuel Macron Sunday afternoon as tensions continue to flare between Russia and Ukraine.

FILE PHOTO: U.S. President Joe Biden delivers remarks on the administration's coronavirus disease (COVID-19) surge response in the South Court Auditorium at the White House in Washington, U.S., January 13, 2022. REUTERS/Kevin Lamarque/File Photo

President Joe Biden (Reuters)

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The move comes after the Kremlin lashed out at NATO Sunday after Russian President Vladimir Putin's call with Macron, with the Russian leader accusing NATO of further enflaming tensions by providing Ukraine with military assistance.

"Serious concern was expressed over the sharp deterioration of the situation on the line of contact in the Donbass," read Russia's summary of Putin's call with Macron. "The president of Russia noted that the reason for the escalation is the provocations of the Ukrainian security forces. Attention is drawn to the ongoing pumping by the NATO countries of Ukraine of modern weapons and ammunition, which is pushing Kyiv towards a military solution to the so-called Donbass problem."

Vladimir Putin

Russian President Vladimir Putin (Yuri Kochetkov/Pool)

The call highlights NATO fears that Putin could use tensions on Ukraine's eastern frontier as a pretext for an invasion of the country, which Biden has warned could happen within days.

"As of this moment, I’m convinced that he’s made the decision," Biden said Friday of Putin's intentions to invade Ukraine. "We have reason to believe that."

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President Biden

President Biden (AP Photo/Evan Vucci)

Biden acknowledged that it was "hard to read" Putin's mind, but noted that U.S. intelligence shows that Russia is set on using a "false flag" operation as a justification to invade a country Putin has long believed belongs under Russian control.

But the president has also stressed that he believes "diplomacy is always a possibility" until the Russian military crosses into Ukraine.