US President Joe Biden has shaken hands with Rishi Sunak on the runway at RAF Aldergrove near Belfast after landing in Northern Ireland to mark the 25th anniversary of the Good Friday Agreement.
The policing operation around Mr Biden’s visit to Northern Ireland will be the biggest in nearly a decade, at an estimated cost of around £7m.
Around 300 officers from other parts of the UK will travel to the area to help police a series of events to mark the anniversary.
Mr Biden is on a four-day visit to the island of Ireland where he said he wants underscore “the US commitment to preserving peace”.
Live: Joe Biden lands in Northern Ireland for historic visit
Mr Biden and the prime minister will hold a bilateral meeting on Wednesday.
The leaders of Northern Ireland’s five main political parties will then have the opportunity to engage with Mr Biden before he speaks at Ulster University.
His remarks at the university will commemorate the Good Friday Agreement.
Mr Biden will then travel across the border to Ireland where he will tour Carlingford Castle in County Louth, an area to which he has traced his roots.
Then it’s off to Dublin, where he is expected to visit Irish President Michael D Higgins on Thursday.
Mr Biden will take part in a tree-planting ceremony and ringing of the Peace Bell at the president’s official residence, Aras an Uachtarain.
Following that ceremony, he will meet again with Irish Prime Minister Leo Varadkar and address the Irish parliament.
A banquet dinner at Dublin Castle will follow on Thursday evening.
The president’s trip will end with a visit to County Mayo on Friday, where he has connected with distant cousins.
A descendant of Irish immigrants to the United States, Mr Biden will deliver remarks at St Muredach’s Cathedral in Ballina, County Mayo, to which his great-great-great-grandfather Edward Blewitt sold 27,000 bricks in 1827.
The bricks were used to build the cathedral and their sale helped to fund Mr Blewitt’s passage to the US with his family in 1851.
Asked what his top priority was for the trip as he was about to board Air Force One to travel to Northern Ireland, the president said: “Make sure the Irish accords and the Windsor agreement stay in place; keep the peace. That’s the main thing.”
The president’s trip comes at an uncertain time for Northern Ireland, where power sharing in Stormont is still on hold and the terror threat has been raised to severe – meaning an attack is highly likely.
Mr Biden’s arrival came hours after four suspected pipe bombs were found by police in a cemetery in Northern Ireland.
Officers sealed off the City Cemetery in Creggan, Derry/Londonderry, on Tuesday following the discovery of a suspicious device.
There were some disturbances on Easter Monday when petrol bombs were thrown at an armoured police Land Rover in Creggan during what police described as an “unnotified” march by dissident republicans.
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Good Friday Agreement 25 years on – how it led to peace, hope and paralysis
Police in Northern Ireland condemned the incident as “senseless and reckless” and said its officers will review footage of the incident as part of an investigation into potential terrorism offences.
It came as the world marked the 25th anniversary of the Good Friday Agreement, also known as the Belfast Agreement, which has been credited with bringing peace to the region after decades of sectarian conflict.
It is also the day that dissident republicans traditionally mark the anniversary of the Easter Rising rebellion against British rule in 1916.
Elsewhere, Mr Sunak issued a renewed call to get Stormont back up and running after a year of stalemate, saying: “We must get on with the business of governance”.
His meeting with Mr Biden comes just weeks after his Windsor Framework passed through parliament.
UK and EU officials have since signed off on the new Brexit deal, despite opposition from the Democratic Unionist Party (DUP), which is preventing the return of the Northern Ireland Assembly.
It was the DUP’s objection to the previous Northern Ireland Protocol, which the Windsor Framework replaces, that resulted in Stormont’s collapse.