US President Joe Biden and Russian leader Vladimir Putin will hold a video call on Tuesday, with the two leaders set to discuss the tense situation in Ukraine.
“Mr Biden will underscore US concerns with Russian military activities on the border with Ukraine and reaffirm the United States' support for the sovereignty and territorial integrity of Ukraine,” White House spokesperson Jen Psaki said.
She said other topics would include “strategic stability, cyber and regional issues.”
The two will also talk about bilateral ties and the fulfilment of agreements reached at their Geneva summit in June, the Kremlin said on Saturday.
“The conversation will indeed take place on Tuesday,” Kremlin spokesman Dmitry Peskov said. “Bilateral relations, of course, Ukraine and the realisation of the agreements reached in Geneva are the main (items) on the agenda,” he said.
The exact timing of the call was not disclosed.
More than 94,000 Russian troops are believed to be massed near Ukraine's borders. Ukraine defence Minister Oleksii Reznikov said on Friday that Moscow may be planning a large-scale military offensive at the end of January, citing intelligence reports. US officials have come to similar conclusions, they said.
Mr Biden, meanwhile, has rejected Russian demands for security guarantees in the region.
“My expectation is we're going to have a long discussion with Putin,” Mr Biden told reporters on Friday as he departed for a weekend trip to Camp David. “I don't accept anybody's red lines,” he said.
The US president said he and his advisers were preparing a comprehensive set of initiatives aimed at deterring Putin from an invasion. He did not give further details, but the administration has discussed partnering with European allies to impose more sanctions on Russia.
US defence Secretary Lloyd Austin separately said that Washington was committed to ensuring that Ukraine had what it needed to protect its territory.
Mr Austin added that there was a lot of space for diplomacy and leadership to work on Ukraine.
At the same conference, James C. McConville, chief of staff of the US Army, on Saturday referred to estimates of 95,000 to 100,000 Russian troops on the border with Ukraine.
“I don't know what they are going to do, but I am very, very concerned,” Mr McConville said.
Moscow accuses Kyiv of pursuing its own military build-up. It has dismissed as inflammatory suggestions that it is preparing for an attack on its southern neighbour and has defended its right to station troops on its own territory as it sees fit.
US officials say they do not know yet what Putin's intentions are, including whether Putin has made a decision to invade Ukraine.
'Severe costs and consequences'
Washington's relations with Moscow have been deteriorating for years, notably with Russia's 2014 annexation of Crimea from Ukraine, its 2015 intervention in Syria and US intelligence charges of meddling in the 2016 election won by now-former President Donald Trump.
But they have become more volatile in recent months.
The Biden administration has asked Moscow to clamp down on ransomware and cyber crime attacks emanating from Russian soil, and in November charged a Ukraine national and a Russian in one of the worst ransomware attacks against American targets.
Russia has repeatedly denied carrying out or tolerating cyber attacks.
The two leaders have had one face-to-face meeting since Biden took office in January, sitting down for talks in Geneva in June. They last talked by phone on July 9. Biden relishes direct talks with world leaders, seeing them as a way to lower tensions.
US Secretary of State Antony Blinken warned Russian Foreign Minister Sergey Lavrov in Stockholm earlier this week that the United States and its European allies would impose “severe costs and consequences on Russia if it takes further aggressive action against Ukraine.”
