Britain's top diplomat said Tuesday that talks with the European Union had led to improvements in a row over Northern Ireland that had set off a political crisis, as the United States encouraged progress.

On leaving the European Union, Britain agreed to a protocol that lets Northern Ireland remain in the EU common market -- avoiding the reimposition of a hard border in Ireland that could have scuttled the peace that has largely prevailed since the 1998 Good Friday accord.

But disagreements on the implementation over trade prompted pro-UK parties to walk out of the Northern Ireland assembly last year and there has been no breakthrough on restoring a power-sharing government ahead of a Thursday deadline.

On a visit to Washington, British Foreign Secretary James Cleverly indicated progress but declined to predict if institutions would be up and running again by the accord's 25th anniversary in April.

"The conversation is happening in good faith, very discreetly and that discretion I think has helped us make real improvements," Cleverly said at the Center for Strategic and International Studies.

"We want to get this result as soon as possible," he said.

Cleverly later met with Secretary of State Antony Blinken who stressed the "unequivocal support" for the Good Friday accord by President Joe Biden, who is known for his pride in his Irish heritage.

The agreement "over the past 25 years has been integral to preserving peace, stability and prosperity for the people of Northern Ireland," Blinken told a joint news conference.

"The United States believes that there must be a negotiated settlement to the implementation of the Northern Ireland Protocol that's acceptable to all sides, and we're heartened that, in recent days, the United Kingdom and the European Union have made substantive progress."

Cleverly on Monday held new virtual talks with the European Union on the protocol. A week earlier, the two sides said they had reached an agreement regarding information technology systems.

The Conservative diplomat voiced solidarity for Northern Ireland businesses which say they are having trouble buying from the British mainland.

"This is about making sure that a part of my country is able to be a meaningful part of my country. Northern Ireland is part of the United Kingdom," he said.