Boris Johnson has become the first world leader outside North America to speak to Joe Biden after a call was brought forward.
The British Prime Minister has been photographed in good spirits speaking to his counterpart across the Atlantic on Saturday evening.
Long-time public servant Biden entered the White House on Wednesday, bringing to an end Donald Trump’s controversial time in office.
The former senator and VP to Barack Obama was understood to be planning to call fellow leaders on Monday and Tuesday before opting to call Downing Street early.
Downing Street said Mr Johnson congratulated Mr Biden on his inauguration, and that the two leaders looked forward to “deepening the close alliance” between their nations.
A No 10 spokesman said that the Prime Minister warmly welcomed Mr Biden’s decision to rejoin the Paris Agreement on climate change and the World Health Organisation.
“The Prime Minister praised President Biden’s early action on tackling climate change and commitment to reach net zero by 2050,” the spokesman said.
“Building on the UK and US’ long history of cooperation in security and defence, the leaders re-committed to the Nato alliance and our shared values in promoting human rights and protecting democracy.
“They also discussed the benefits of a potential free trade deal between our two countries, and the Prime Minister reiterated his intention to resolve existing trade issues as soon as possible.
“The leaders looked forward to meeting in person as soon as the circumstances allow, and to working together through the G7, G20 and Cop26 this year.”
The PM tweeted: “Great to speak to President Joe Biden this evening.
“I look forward to deepening the long-standing alliance between our two countries as we drive a green and sustainable recovery from Covid19.”
Mr Johnson’s predecessor Theresa May was 11th on President Trump’s call list after he won the election in November 2016.
She fell behind the leaders of Egypt, Saudi Arabia, Mexico, Japan, India, Turkey, Israel, South Korea, Australia and Ireland.