Drawing on his own experiences before and after the 1991 Gulf War, Mr Bush Sr said that the brief flowering of hope for Arab-Israeli relations a decade ago would never have happened if America had ignored the will of the United Nations.

He also urged the President to resist his tendency to bear grudges, advising his son to bridge the rift between the United States, France and Germany.

“You’ve got to reach out to the other person. You’ve got to convince them that long-term friendship should trump short-term adversity,” he said.

The former President’s comments reflect unease among the Bush family and its entourage at the way that George W. Bush is ignoring international opinion and overriding the institutions that his father sought to uphold. Mr Bush Sr is a former US Ambassador to the UN and comes from a family steeped in multi-lateralist traditions.

Although not addressed to his son in person, the message, in a speech at Tufts University in Massachusetts, was unmistakeable. Mr Bush Sr even came close to conceding that opponents of his son’s case against President Saddam Hussein, who he himself is on record as loathing, have legitimate cause for concern.

He said that the key question of how many weapons of mass destruction Iraq held “could be debated”. The case against Saddam was “less clear” than in 1991, when Mr Bush Sr led an international coalition to expel invading Iraqi troops from Kuwait. Objectives were “a little fuzzier today”, he added.

After the Gulf War, Mr Bush Sr steered Israel and its Arab neighbours to the Madrid conference, a stepping stone to the historic Israeli-Palestinian Oslo accords, in much the same way that the present President has talked about the removal of Saddam as opening the way to a wider peace in the region.

In an ominous warning for his son, Mr Bush Sr said that he would have been able to achieve nothing if he had jeopardised future relations by ignoring the UN. “The Madrid conference would never have happened if the international coalition that fought together in Desert Storm had exceeded the UN mandate and gone on its own into Baghdad after Saddam and his forces.”

Also drawing on the lessons of 1991, he said that it was imperative to mend fences with allies immediately, rather than waiting until after a war. He had been infuriated with the decision of King Hussein of Jordan to side with Saddam rather than the US, but while criticising the Jordanian leader in public and freezing $41 million in US aid, he also passed word to King Hussein that he understood his domestic tensions.

Mr Bush Jr, who is said never to forget even relatively minor slights, has alarmed analysts with the way in which he has allowed senior Administration figures such as Donald Rumsfeld, the Defence Secretary, aggressively to criticise France and Germany.

There are, however, signs that Mr Bush Sr’s message may be getting through.

Father and son talk regularly and it was, in part, pressure from Mr Bush Sr’s foreign policy coterie, that helped to persuade the President to go to the UN last September.