US president Joe Biden has said he is worried that the Russian leader, Vladimir Putin, does not have a way out of the Ukraine war.
The president said he was "confident that Putin believed he could break up Nato, that he believed he could break the European Union".
Speaking at a political fundraising event in Maryland on Monday night, Mr Biden said he had spent "well over 150 hours trying to keep the other heads of state on the same page and keep us together, constantly making sure we're on the same page [regarding the Russian invasion of Ukraine]".
The president suggested Mr Putin had miscalculated in his predictions on the reaction to his invasion of Ukraine.
"I'm confident Putin believed that he could break up Nato. I'm confident he believed he could break up the European Union, that we couldn't hold it together. But we're doing it. It's not easy, and a lot of other countries have to make greater or lesser sacrifices than we. But it's not easy."
“But it’s critically important because Putin is a . . . very, very, very calculating man. And the problem I worry about now is that he doesn’t have a way out right now, and I’m trying to figure out what we do about that. But that’s a different story.”
On Monday, the US president signed into law new legislation aimed at speeding up the delivery of weapons to Ukraine in its fight against the Russian invasion.
The legislation is essentially an updated version of the lend-lease programme introduced to allow the US to assist its allies during the second World War.
Mr Biden also said the US would run out of money to provide weapons and other support for Ukraine in less than a fortnight without further funding authorised by the US Congress.
He said in a statement that the need to provide a new package of military, economic, and humanitarian assistance to Ukraine was urgent. He said there appeared to be support for his proposals for a new package of measures for Ukraine among politicians on Capitol Hill and he urged them to approve the plan quickly.
Separately, it emerged that Mr Biden was privately furious at leaks last week about the American intelligence assistance to Ukraine that led to the deaths of Russian generals and the sinking of the cruiser Moskva.
The president was concerned that it would provoke escalation of the conflict by Russia which the Biden administration has sought strongly to avoid.
US media reported that the president had called defence secretary Lloyd Austin, director of national intelligence, Avril Haines, and CIA director William Burns to criticise the leaking of the information.
The White House said at a briefing on Monday that "the president was displeased with the leaks".
“His view is that it was an overstatement of our role – an inaccurate statement – and also an understatement of the Ukrainians’ role and their leadership. And he does not – did not felt they were constructive.”