US President Joe Biden has said he thinks his Russian counterpart Vladimir Putin will "move in" on Ukraine, but does not want "full-blown war".

Asked at a news conference about the threat of a Russian invasion, he said: "My guess is he will move in, he has to do something.".

In a statement issued on Wednesday night, White House press secretary Jen Psaki said: "If any Russian military forces move across the Ukrainian border, that's a renewed invasion, and it will be met with a swift, severe, and united response from the United States and our Allies.".

Russia has made a raft of demands to Western governments, including that Ukraine should never join Nato and that the defensive alliance's military activities should be limited in member states including Poland.

Test the United States and Nato as significantly as he can.

"He's never seen sanctions like the ones I promised will be imposed if he moves," Mr Biden said, adding that the exact level of punishment would depend on the scale of any invasion.

Asked how concerned he was about the possibility of a conflict in Ukraine sucking in neighbouring Nato states, he said: "The only war that is worse than one that's intended is when it's unintended and what I'm concerned about is that this could get out of hand.

He also said it was "very important" Nato allies stay on the same page in the face of a potential Russian attack.

Speaking in Kyiv, Mr Blinken said Russia could attack Ukraine "on very short notice" and warned again of tough sanctions if it did.

Now the president has clearly stated what everyone privately knew - that Nato is united on what the response should be to an invasion, but not to an incursion: "There are differences in what countries are willing to do depending on what happens.