Joe Biden has said the "enemies of peace will not prevail" in Northern Ireland as he made a historic address in Belfast.
The US President, visiting Northern Ireland to mark 25 years since the Good Friday Agreement, said the political response to the shooting of Detective Chief Inspector John Caldwell showed the province "will not go back".
He told an audience at Ulster University: "Northern Ireland will not go back, pray God.
"The attack was a hard reminder there will always be those who seek to destroy, rather than rebuild.
"But the lesson of the Good Friday Agreement is this - at times when things seem fragile or easily broken, that is when hope and hard work are needed the most."
Mr Biden called on Northern Irish leaders to break the deadlock which has seen effective government in the province collapse.
The powersharing executive at Stormont when the DUP walked out last year in protest over the Northern Ireland Protocol in Boris Johnson's Brexit deal.
He said: "I hope the assembly and the executive will soon be restored. That's a judgment for you to make, not me.
"I hope it happens, along with the institutions that help facilitate north-south and east-west relations, all of which are vital pieces of the Good Friday Agreement."
The US President said compassion "had changed how this entire region sees itself".
He said: "This place is transformed by peace, made technicolour by peace, made whole by peace.
"So today, I come to Belfast to pledge for all the people of Northern Ireland, the United States of America will continue to be your partner in building the future the young people of our world deserve.
"It matters to us, to Americans, and to me personally. It genuinely matters.
"So let's celebrate 25 extraordinary years by recommitting to renewal, repair, by making this exceptional peace a birth right of every child in Northern Ireland for all the days to come.
"That is what we should be doing, God willing you'll be able to do it."
The US President earlier met Rishi Sunak for a brief chat.
Following their talk, Mr Sunak described the UK's relationship with the US as being "in great shape", saying they were "very close partners and allies".
He said he had a "very good discussion" with Mr Biden in Belfast.
Mr Sunak said they discussed economic investment in Northern Ireland as well as foreign policy issues.
"That comes on the back of a meeting I had with him last month in the US, I'm seeing him again next month at the G7 and then I'm going to Washington in June; we're very close partners and allies, we co-operate on a range of things, whether that's supporting Ukraine or economic security," he said.
"I think actually the relationship is in great shape, and the President and I have lots that we're working on together."
