Sir Keir and Joe Biden will meet at the Nato Summit in Washington next week.
After Mr Biden congratulated the new PM yesterday afternoon, a Downing Street spokesperson said one of the issues they had spoken about was Northern Ireland.
“The leaders reflected on their shared commitment to protecting the gains of the Belfast (Good Friday) Agreement,” they said.
First Minister Michelle O’Neill last night said she had raised health funding and Casement Park with Sir Keir when they spoke yesterday evening in the wake of Labour’s election victory.
“We discussed the need to reset British-Irish relations and in particular with our local Executive,” she said in a post on X.
“I strongly made the case for fair funding to be urgently provided for health, education, and public services here.
“The cuts that our people and public services have endured under a Tory government for over a decade must end now.
“I also reiterated the necessity for immediate funding to be released to build Casement Park, allowing us to seize the enormous economic opportunities created by Euro 2028.
“I urged the Prime Minister to follow through on his commitments to bin the Tories’ shameful Legacy Act which has failed victims and survivors.”
Earlier, a leading Troubles victims’ group welcomed the appointment of Hilary Benn as Northern Ireland’s new Secretary of State, as they looked forward to the repeal of the controversial Legacy Act.
Mr Benn had been serving as the shadow secretary since 2023 and has previously said a Labour government would repeal the controversial Legacy Act, which sought to end legal proceedings linked to the Troubles by granting conditional immunity for perpetrators of Troubles crimes.
Labour Party MP Hilary Benn arrives at 10 Downing Street
It was widely opposed by all main political parties in Northern Ireland.
The Leeds MP was also vocal in urging the powersharing institutions to be revived during the three-year hiatus.
Wave Trauma Centre last night said it was “looking forward to Hilary Benn tackling some of the big issues facing victims and survivors, starting with repealing the hated Legacy sham with its zero credibility and extending the lump sum deadline for injured victims payments.
“A focus on the bereaved is now needed. Many congratulations on your appointment.”
A host of Mr Benn’s Tory predecessors have now left or been ejected from the Commons.
Chris Heaton-Harris and Brandon Lewis did not stand, while Shailesh Vara and Theresa Villiers lost their seats. However, Julian Smith and Karen Bradley were re-elected.
Prominent Northern Ireland minister Steve Baker, who had been hinting at a run at the Tory leadership just days ago, also lost his seat.
He said yesterday being an MP is a “dreadful job”.
Speaking on LBC, Mr Baker said: “I fought this campaign to win, I wanted to win, I wanted to go ahead and do my duty but Nick, I have to tell you, it is a dreadful job and I am thank God I’m free. I will not be back.
“I’ve been threatened with hanging, my throat slit, acid.”
He added: “Thank God it’s over.”
Meanwhile, the Taoiseach said Sir Keir’s victory offered the chance for “a great reset” in Anglo-Irish relations. The relationship had suffered in recent years in disputes over Brexit and the Legacy Act.
“Today is about looking forward,” Mr Harris said as he addressed reporters at Government Buildings in Dublin.
“It’s about realising the full potential of that relationship between Taoiseach and Prime Minister and between our governments. I know that Keir Starmer and I share a desire for it to go from strength to strength. It is time for a great reset.”
Meanwhile, Rachel Reeves was confirmed as Britain’s first woman chancellor, Angela Rayner is Sir Keir’s Deputy Prime Minister and retained the levelling up, housing and communities brief, and Yvette Cooper is Home Secretary.
David Lammy was appointed Foreign Secretary, putting to bed some speculation over whether he would get the post he shadowed in opposition.
The first surprise in the assembly of the Labour leader’s top team was the promotion of Lisa Nandy to Culture Secretary, after the holder of the brief in his shadow cabinet, Thangam Debbonaire, lost her seat to the Green Party.
Otherwise, the Cabinet mirrors Sir Keir’s shadow team, including Pat McFadden, who played a central role in shaping Labour’s election campaign, being named Chancellor of the Duchy of Lancaster, John Healey Defence Secretary, Shabana Mahmood Justice Secretary, Wes Streeting Health Secretary, Bridget Phillipson Education Secretary and Ed Miliband Energy Secretary.
Lucy Powell will be Leader of the House of Commons, while Baroness Smith of Basildon will be Leader of the House of Lords.
In his first speech on Downing Street, Sir Keir said the British people had voted “decisively for change”.
Sir Keir said the country could “move forward together” as Labour took office following 14 years of Conservative rule.
He said: “Now our country has voted decisively for change, for national renewal and a return of politics to public service.
“When the gap between the sacrifices made by people and the service they receive from politicians grows this big, it leads to a weariness in the heart of a nation, a draining away of the hope, the spirit, the belief in a better future.
“But we need to move forward together. Now this wound, this lack of trust can only be healed by actions not words, I know that.
“But we can make a start today with the simple acknowledgement that public service is a privilege and that your government should treat every single person in this country with respect.”
He said “my Government will serve you, politics can be a force for good”, adding: “The work of change begins immediately, but have no doubt, we will rebuild Britain.”
Following a brutal set of results for the Conservatives, Rishi Sunak announced he would quit as Tory leader and used his final speech in Downing Street to apologise to the British people and the Conservative Party.