US President Joe Biden has spoken by phone to Liz Truss to congratulate her on becoming Britain's new prime minister, with both vowing to strengthen their relationship as they stand together against Russia.
"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," Biden said in a tweet on Tuesday.
The two leaders could meet as soon as the United Nations General Assembly later this month.
The prime minister's office said in a statement they discussed deepening cooperation on NATO and the AUKUS security agreement set up last year as a counter to China.
Truss looks forward to "working closely with President Biden as leaders of free democracies to tackle shared challenges, particularly the extreme economic problems unleashed by Putin's war," the British statement said.
Truss won a leadership race for the governing Conservative Party on Monday and took over as prime minister on Tuesday, as Britain faces its most daunting set of challenges in decades.
The so-called special relationship between the United States and Britain has maintained solid continuity in recent years, despite frictions between then-president Donald Trump and then-prime Minister Theresa May.
Washington and London have been aligned on helping Ukraine in its war against Russia and in countering China's influence in the Pacific. But a bilateral trade deal that some British officials hoped could offset trade and economic upheaval after Brexit has yet to materialise under Biden.