The President of the European Parliament, Mr Pat Cox, said yesterday that a second No vote in the forthcoming Nice referendum could diminish the Republic's influence in Europe and the United States, and that he would be returning to Ireland to vigorously campaign for a Yes vote when the date was announced.

Speaking after giving an address to the US-Ireland Business Summit in Washington, Mr Cox said the Republic found itself in a paradoxical situation in Europe.

Many small states were about to join and saw the Republic as their role model.

He had made official visits to 10 aspirant states and found a great amount of positive fascination in the Republic's success but complete perplexity about "how come we did it to them" by rejecting the Treaty that provided for their admission.

He said one of their fears was maybe the Republic had taken a selfish turn - "we've had our cake and we ate it. Let's draw down the shutters."

At the last referendum enough people who were pro-European felt sufficiently confused to stay at home rather than vote No.

This time it was there to be won. It could not be won without conviction and campaigning, which were conspicuously absent in the last referendum.

His message would be that "there is a lot at stake about our ability to influence people in our own interests. Earlier on, in the 1970s, when we made the decision to join, we escaped from sovereignty with isolation, to sovereignty with inter-dependence.

"In crossing that bridge we crossed from stagnation to opportunity and we owe it to ourselves and our children to stick with the opportunity and the bridge that brought it."

Taking the Republic's external relations in its broadest sense, "irrespective of who was in government, we have been a predictable strategic partner with total reliability and a No vote would represent the first time in a long stretch when we began to unbundle the things for which we had strategic reliability.

"So I'm not one of those with the theory that, the day after, the sky will fall but when you remove from strategic certainty and reliability you remove something very valuable."

Addressing the business leaders at the business summit, Mr Cox played down the trade disputes between the US and Europe, saying that the two entities had a unique $1 trillion (€1.01 trillion) trade relationship, only 4 per cent of which was affected by disputes.

The European Union's main concerns were to bring about compliance not sanctions, he said.

Mr Cox added that he would appeal to Congress that "this is a moment where people who believe in free trade have to take a vigorous stand".

Asked about EU attitudes to possible US action against Iraq, Mr Cox said: "The European Union strongly believes that unilateral pre-emptive action carries very heavy risks" but there was also an understanding "that inaction carries grave risks".

He commended President Bush for beginning to connect with allies and going to the United Nations "and, as a European politician, I would commend that, if we understand that in international politics, at the limit you have force and the rule of law."