Sinn Féin president Mr Gerry Adams was reported tonight to have told colleagues on the Sinn Féin national executive of his "deep concern" about the effect of Mr Trimble's resignation plan on rank-and-file republicans.
In a strongly worded statement after a meeting in Dublin, the party claimed the Ulster Unionist leader's move had undermined Mr Adams's efforts on disarmament.
Noting changes in the international decommissioning body's remit last May had presented an opportunity for progress on the arms issue, a party spokesman stressed the significance of contacts between the IRA and the de Chastelain Commission.
"No-one should underestimate the importance of this engagement which in itself is an advance which needs to be worked on," the spokesman said.
"This is a process but what is clear is that David Trimble's latest move has damaged those efforts.
"There is no doubt that Sinn Féin is committed to making this work. Whatever the effect of David Trimble's threatened resignation on unionism and his role as UUP leader, he has undermined Gerry Adams' efforts."
PA