Russian President Vladimir Putin is demanding a legally binding guarantee that NATO will not expand east - including to Ukraine - and plans to raise the issue in an upcoming phone call with President Biden, according to the Kremlin.
Why it matters: Russia has massed more than 94,000 troops on the border with Ukraine and could be preparing for a large-scale invasion at the end of January, Ukraine's defense minister said Friday.
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What they're saying: Biden told reporters Friday that his top national security officials are "putting together what I believe will be the most comprehensive and meaningful set of initiatives to make it very, very difficult for Mr. Putin to go ahead and do what people are worried he may do."
Driving the news: Putin has blamed the heightened tensions on increased NATO activity near Russia's borders, including Western support for Ukrainian government forces fighting Russian-backed separatists in the Donbas region.
Secretary of State Antony Blinken met with Russian Foreign Minister Sergey Lavrov in Stockholm on Thursday to call for de-escalation.
He warned that the U.S. and its allies would "impose severe costs and consequences" - including unprecedented economic sanctions - if Russia took further action.
Lavrov shot back that NATO was "playing with fire" with its exercises near Russian borders and that Moscow was prepared to take "retaliatory measures to correct the military-strategic balance."
The big picture: NATO promised Ukraine membership in the alliance in 2008, but has declined to set out a timeline due to concerns about corruption and the implications of integrating a country that has already been invaded by Russia.
NATO Secretary-General Jens Stoltenberg condemned the Kremlin on Wednesday for suggesting that support for a sovereign country like Ukraine is a "provocation."
"It's only Ukraine and 30 NATO allies that decide when Ukraine is ready to join NATO," Stoltenberg said. "Russia has no veto, Russia has no say, and Russia has no right to establish a sphere of influence to try to control their neighbors."
What to watch: A top foreign policy aide to Putin said Friday that the U.S. and Russia were finalizing the date for a video call with Biden.
In addition to guarantees against NATO's eastward expansion, Putin will seek a ban on "weapons systems that would threaten us on the territories of neighboring countries, including Ukraine," the aide said.
It will be the second time Biden has spoken to Putin since June, when the two leaders met in Geneva as part of Biden's push for a more "stable" and "predictable" relationship with Russia.