The Kremlin on Monday said that questions about the situation in Ukraine and NATO’s advancement will be discussed when Presidents Joe Biden and Vladimir Putin speak in a video call Tuesday. Tensions between the United States and Russia have escalated over a Russian troop buildup on the Ukrainian border that’s seen as a sign of a potential invasion.

“They will need to discuss how the understandings they reached in Geneva are being implemented, to review what is being fully implemented, and what needs extra work,” Kremlin spokesperson Dmitry Peskov said.

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Biden will press US concerns about Russian military activities on the border and “reaffirm the United States’ support for the sovereignty and territorial integrity of Ukraine,” White House press secretary Jen Psaki had said on Saturday. 

Putin will come to the call with concerns of his own and intends to express Russia’s opposition to any move to admit Ukraine into the NATO military alliance. Kremlin spokesman Dmitry Peskov said “the presidents will decide themselves” how long their talk will last.

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The last known call between the leaders was in July, when Biden pressed Putin to rein in Russia-based criminal hacking gangs launching ransomware attacks against the United States. Biden said the U.S. would take any necessary steps to protect critical infrastructure from such attacks.

“Of course it (the agenda) is bilateral relations, which remain in quite a lamentable state. And then it’s the questions that loom large on the agenda. Primarily tension around Ukraine, the theme of NATO advancement towards our borders, and President Putin’s initiative about security guarantees,” the Kremlin spokesperson added.