The DUP leader, the Rev Ian Paisley, is expected to boycott President George W. Bush's St Patrick's Day reception in the White House today.
Dr Paisley is reported to object to attending the reception on the grounds that President Bush wants to pose with all of the North's political leaders, including the Sinn Féin president, Mr Gerry Adams, for photographs.
While officials behind the scenes were trying to work out a compromise where the DUP leader would attend the reception but not the photo opportunity, they were not hopeful that such a compromise would be found.
Dr Paisley was scheduled to arrive in the US late last night.
The First and Deputy First Ministers, Mr David Trimble and Mr Mark Durkan, arrived in Washington yesterday to carry out a series of engagements during their three-day visit.
These will include high-level meetings with a number of representatives of the US administration, among them the Secretary of State, Gen Colin Powell.