Sinn Féin's Martin McGuinness has expressed his concern at the reported refusal by the United States to grant a visa to the senior party representative Rita O'Hare.
Both met the US Ambassador to Ireland, James Kenny, this morning to update him on the peace process.
Ms O'Hare was due to accompany Mr McGuiness to Washington next Thursday, where he is expected to meet US Congressmen.
It is understood that a visa has been denied. The US State Department would not confirm or deny if this was the case, citing confidentiality.
However, according to one report, it was because of an unscheduled trip she made to Florida during a visit earlier this year.
On St Patrick's Day she had accompanied the party President, Gerry Adams, when he met the Taoiseach and Minister for Foreign Affairs in Washington.
It is understood the US Special envoy to the North, Mitchell Reiss, took a ten-minute phone call yesterday from one senior Irish American Congressman who expressed his disagreement with the decision.