The UUP leader warned that John Major's Government "need not look to us for support" if it started to backslide on the key issue of requiring IRA weapons to be decommissioned as the talks, due to start on 10 June, progressed.
The warning came amid Unionist fears that the separation of the planned talks into different strands, as sought by the Irish government, will break any link between the progress of political talks and the handing in of republican weapons.
Mr Trimble strongly denied on the BBC Radio 4 programme Today that he was adopting a hardline posture in advance of Northern Ireland elections to a peace forum, which will precede the talks.
He said his threat on Tuesday to pull down the Government if it broke undertakings over the ceasefire and decommissioning had been "serious".
He said: "What we have detected in the past few days are signs of a familiar old Irish stitch- up. We've been here regularly in the last 10 years where secret deals done between No 10 and the Irish government are imposed upon us. This is happening not just, we feel, with regard to the details of the talks. We see it happening again and we're blowing the whistle."
His remarks came as Dick Spring, the Irish Foreign Minister and Sir Patrick Mayhew, the Northern Ireland Secretary, prepared yesterday to meet in London to try and make progress on the format or the talks.
Mr Trimble warned that the UUP would "not support an administration that is doing serious damage to the United Kingdom". He added: "What we must do is to make it absolutely clear to the terrorists that terrorism will not work."
Meanwhile, Robert McCartney, the Independent UK Unionist MP for North Down, who had an 80-minute meeting with Mr Major yesterday, said that the Prime Minister now knew that he was "dealing with a professional team of negotiators who know their business."Reuse content