Biden lands in Belfast with vow to 'keep the peace'

US President Joe Biden landed in Northern Ireland on Tuesday, hoping to help maintain the fragile peace brokered 25 years ago after decades of sectarian violence over British rule.

Before boarding Air Force One, Biden, 80, said the priority for his trip was "to keep the peace" and bring an end to the protracted political deadlock caused by opposition among pro-UK parties to post-Brexit trading rules.

UK Prime Minister Rishi Sunak met Biden on the tarmac when he touched down in the Northern Irish capital, just 24 hours after the landmark anniversary of the Good Friday/Belfast Agreement.

But security remains a concern.

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On Monday, masked youths pelted police vehicles with petrol bombs during an illegal march by dissident republicans in Londonderry, which is also known as Derry.

Despite the scenes, US officials said Biden was "very excited for this trip".

"We'd like to see the national assembly (in Belfast) returned, clearly," National Security Council spokesman John Kirby told reporters en route to Belfast, with the Stormont legislature currently suspended.

"The message is twofold. It's congratulations on 25 years of the Good Friday agreement... (and) to talk about the importance of trying to work on trade and economic policies that benefit all communities as well as the United States," he said.

Biden will deliver remarks Wednesday at Ulster University in Belfast, set to focus on the economic promise of inward investment if the peace endures.

He will also meet the leaders of Northern Ireland's main political parties, the White House said, with reports he will press the pro-UK Democratic Unionist Party (DUP) to resume power-sharing.

Devolved government in Belfast is a key plank of the peace accords but it collapsed 14 months ago over the party's trenchant opposition to post-Brexit trade arrangements in Northern Ireland.

Biden, who has Irish ancestry, will also travel south to Ireland for a three-day visit, in part tracing his family history.

The trip will include an address to a joint sitting of Ireland's parliament and "celebrate the deep, historic ties" the country shares with the United States, the White House says.

Northern Ireland has been significantly reshaped since unionist parties wanting to remain part of the UK and nationalists favouring reunification with Ireland struck the peace deal on April 10, 1998.

But a quarter-century on, the post-Brexit trading situation and demographic shifts are prompting fresh political instability and violence from hardliners on both sides.

"While it is time to reflect on the solid progress we have made together, we must also recommit to redoubling our efforts on the promise made in 1998 and the agreements that followed," Sunak said to mark Monday's anniversary.

In Dublin, Biden will meet Irish President Michael Higgins and the Taoiseach (prime minister) Leo Varadkar on Thursday, when he will also take part in peace ceremonies, address the Irish parliament and attend a banquet dinner at Dublin Castle.

During a trip to County Mayo in northwest Ireland on Friday, Biden will visit his ancestral hometown of Ballina and meet distant cousins.

The US president is due to address thousands in the place that his family left in the mid-19th century -- when the country was ravaged by famine -- before they eventually settled in blue-collar Scranton, Pennsylvania.

Biden heads home Friday, with Northern Ireland continuing its peace accord commemorations the following week, including a three-day conference starting April 17 hosted by former US secretary of state Hillary Clinton.

Her husband, Bill Clinton, played a pivotal role in securing the 1998 deal as US president.

In the years after 1998, Northern Irish republican and loyalist paramilitaries were disarmed, its militarised border was dismantled, and British troops departed.

But the security situation has deteriorated, and UK intelligence services last month raised the province's terror threat level to "severe".

Meanwhile, despite the UK and European Union agreeing in February to overhaul Northern Ireland's contentious post-Brexit trade terms, that new deal -- the Windsor Framework -- is yet to win DUP support.

That is seen as crucial in paving the way for a resumption of power-sharing.

But ex-British prime minister Tony Blair, who helped craft the 1998 peace deal, on Tuesday cautioned Biden against overly pressuring the party when in Belfast.

Hardline DUP lawmaker Ian Paisley Jr said the party was in no mood to be lectured by Biden.

The president's "real Irish visit" was to the Republic, Paisley told TalkTV, adding: "I think this visit (to Belfast) has shown we really don't matter that much."