Canada's decision, announced last week following months of agonising by Prime Minister Paul Martin's minority government, dented hopes that relations frayed over the Iraq war were mended.

White House spokesman Scott McClellan said officials in Washington and Ottawa, and aides to Mexico's President Vicente Fox were prepping talks expected in Mexico City on March 23 on the North America Free Trade Agreement (NAFTA).

"We have a meeting that's going to be coming up with Prime Minister Martin and President Fox. We're still finalizing the details on that meeting," he said.

McClellan denied Canada's announcement on the missile shield would jar cooperation between two giant neighbors, often referred to as joint custodians of the world's longest undefended border.

"We're going to continue to work with Canada and cooperate with them on shared defense priorities," McClellan said. "We have been cooperating on defense issues in the past and we will in the future."

McClellan did not, however, scotch reports that Bush expressed displeasure at the decision by declining to return a call from Martin to explain it: "I'll have to check on that, I don't know if that's the case," he told AFP.

Melanie Gruer, a spokeswoman for Martin, downplayed reports that Bush had deliberately avoided returning the prime minister's call.

"The president has been travelling," she said, adding that Martin's aides understood the pressures on busy leaders' schedules.

But in another sign of US tetchiness over the issue, the State Department said earlier that a visit likely to have been made next month by Secretary of State Condoleezza Rice had not been scheduled.

Rice would have traveled to Canada in the second week of April.

A US official travelling with her in London said on condition of anonymity that Rice's not going there was "in part" due to Canada's refusal to cooperate on missile defense.

State Department spokesman Adam Ereli however later denied in Washington there was any link between Rice's travel schedule and the missile defense issue, calling the idea "inaccurate" and stressing efforts to schedule a meeting between Rice and her Canadian counterpart were ongoing.

White House spokesman Scott McClellan said he talked with the State Department and that "my understanding is there was never a trip scheduled. So there's nothing to postpone when you don't have a trip scheduled."

"Our Ambassador in Canada has expressed our views, as well, and expressed our disappointment. But now we're talking about ways we move forward on our shared priorities," said McClellan.

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