US Secretary of State Antony Blinken warned Friday that any movement of Russian military forces across Ukraine's border would represent 'a renewed invasion' that will be 'met with swift, severe and a united response' from the United States and allies.

Blinken's remarks followed an hour and a half bilateral meeting Friday in Geneva with Russian Foreign Minister Sergei Lavrov, in which the talks tackled the escalation at the Ukrainian border.

Blinken and Lavrov both confirmed that the US had agreed to send written answers to all of Russia's security demands next week.

'I told him that following the consultations that we'll have in the coming days with allies and partners, we anticipate that we will be able to share with Russia our concerns and ideas in more detail and in writing next week, and we agreed to further discussions after that,' Blinken told reporters following his sit-down with Lavrov.

Both sides admitted before their talks that neither was expecting a breakthrough on Russia's security proposals, which the US and allies have deemed nonstarters.

Russia has demanded a pledge that NATO will not allow Ukraine to join the military alliance and won't expand further east.

Speaking at the start of the meeting, Blinken said that Washington is committed to a 'united, swift and severe response' if Moscow commits further aggression against Ukraine.

'We are, all of us, all equally committed to the path of diplomacy and dialogue to try to resolve our differences,' Blinken said.

'But we're also committed, if that proves impossible and Russia decides to pursue aggression against Ukraine, to a united, swift and severe response.' Blinken reiterated he didn't expect the US and Russia to resolve their differences in the meeting but said he hoped to keep a diplomatic path to addressing those issues open.

'We're committed to walking that path and resolving our differences peacefully,' he said.

Blinken's meeting with Lavrov on Friday followed his meetings in Berlin with his German, UK and French counterparts and Kyiv, where he met with Ukrainian President Volodymyr Zelensky.

President Joe Biden on Wednesday predicted that Russia will invade Ukraine but also acknowledged disunity within NATO over how to respond to a 'minor incursion' by Russia, prompted outcry from stunned Ukrainian officials who warned that Biden's comments are a green-light to Russia President Vladimir Putin.

Biden sought to clean up his remarks on Thursday, clarifying his stance on a potential Russian incursion in Ukraine.