Sir Keir Starmer and Emmanuel Macron are plotting to dramatically increase military support for Ukraine before Donald Trump arrives in the White House.

The Prime Minister and French President will meet in Paris today and discuss whether the outgoing US President, Joe Biden, can finally be persuaded to give Kyiv the green light to fire British-made Storm Shadow missiles deep into Russia.

Mr Biden’s national security advisor, Jake Sullivan, has urged Mr Trump not to abandon Ukraine.

Senior figures within the Republican’s team have hinted the US will scale back support for the war-torn nation, with many analysts fearing he will force President Zelensky to accept a loss of land.

But hopes are rising within Whitehall that Mr Biden will allow Ukrainian forces to use Storm Shadow missiles to secure his foreign policy legacy.

A senior source said: “We are very keen to make sure we can make the most of the time between now and Jan 20 [when Mr Trump becomes US president] and not just put everything on hold until the next administration.”

Another source said Mr Biden was expected to “turn on the taps” by handing over more financial aid to Kyiv before he leaves the White House.

Should Kyiv be given permission to fire Storm Shadows deep into Russian territory before Mr Trump took office it would be more difficult for the approval to be reversed.

World leaders are watching nervously for signs of how the President-elect will shift Washington’s policies on Ukraine.

Mr Trump has talked about ending the Ukraine war on “day one”, without specifying how.

The meetings come less than a week after it was confirmed that Donald Trump will be returning to the White House in January having been re-elected US president.

Donald Trump Jr, the president-elect’s son, has ruled out “war hawks” serving in the Cabinet, in another sign a stark change in approach could be coming.

In a post on Instagram on Saturday, he posted a video appearing to mock President Zelensky over losing his American “allowance” when his father returns to the White House.

In the clip, Mr Zelensky looks unhappy alongside Mr Trump with the caption: “POV: You’re 38 days from losing your allowance.”

President Biden, who will meet Mr Trump on Wednesday, will urge him not to abandon Ukraine.

Mr Sullivan said: “President Biden will have the opportunity over the next 70 days to make the case to the Congress and to the incoming administration that the United States should not walk away from Ukraine, that walking away from Ukraine means more instability in Europe.”

Mr Zelensky has been calling for permission to fire the missiles further into Russia for months as it could help stop Russian planes taking off before bombing Ukraine.

Defence Secretary John Healey on Monday insisted he expects the US to stand by Ukraine for “as long as it takes to prevail over (Vladimir) Putin’s invasion” amid questions over the future of US support under Donald Trump.

Me Healey said he thought the president-elect “recognises that countries get security through strength, just as alliances like Nato do” and American “determination” to continue backing Ukraine is “just as strong”.

Asked whether Ukraine‘s safety had diminished since Mr Trump’s election win, Mr Healey told Sky News: “No, I don’t. The US alongside the UK have been two of the leading countries that have been standing by Ukraine, supporting Ukraine, our determination to do so is just as strong.”

He added: “As far as President Trump goes, he recognises that countries get security through strength, just as alliances like Nato do, and I expect the US to remain alongside allies like the UK, standing with Ukraine for as long as it takes to prevail over Putin’s invasion.”

Asked whether the loss of US backing would put us in “a very weak and exposed position”, the Defence Secretary told Sky News: “No, we wouldn’t be in a weak position.

“I don’t expect the US to turn away from Nato. They recognise the importance of the alliance. They recognise the importance of avoiding further conflict in Europe.”

He said the US support for Nato “goes back decades, and that has remained, including through the previous President Trump administration”.

“He pushed, rightly, he pushed European nations to do more, to front Nato better,” Mr Healey added.