US President Joe Biden has congratulated Liz Truss on becoming Prime Minister and vowed to deepen the “special relationship”.

Just as Ms Truss finished her speech and formally entered Downing Street, the US president tweeted: “Congratulations to Prime Minister Liz Truss.

“I look forward to deepening the special relationship between our countries and working in close cooperation on global challenges, including continued support for Ukraine as it defends itself against Russian aggression.”

The White House confirmed that Mr Biden will speak to Ms Truss on Tuesday evening.

US press secretary Karine Jean-Pierre told reporters in the White House: “He’s going to speak to her later today, this afternoon. He’s planning to call her to congratulate her, the new Prime Minister.”

Mr Biden’s tweet was the first public message since Ms Truss was elected as Conservative leader on Monday.

Ms Truss is expected to travel to the US later this month for the United Nations General Assembly, where she will be hoping for her first face-to-face meeting with the president.