The United States is backing Canada's battle to keep the headquarters of the International Civil Aviation Organization in Montreal, providing an influential ally in the effort to win international votes.

The backing of the world's most powerful nation could prove essential in fending off a bid from Qatar to move the ICAO, the United Nations agency that sets international rules for airplane transportation, to Doha in 2016.

The support came as the federal government, Quebec government and mayor of Montreal joined to launch a "Team Montreal" campaign to keep the ICAO – including hinting that they might be willing to sweeten the terms for the agency to counter Qatar's rich package.

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But already, U.S. Ambassador to Canada David Jacobson has made American backing clear: "The U.S. sees no reason to move the ICAO out of Montreal and would not support such a proposal," spokesman Steve Pike told The Globe and Mail.

Qatar's bid is already playing into discontent in the Arab world over Ottawa's pro-Israel position on Palestinian issues. That sentiment has been fuelled by the Harper government's vocal campaign last fall against a Palestinian bid for observer-state status at the UN and by Foreign Affairs Minister John Baird's April 9 meeting with Israeli Justice Minister Tzipi Livni in east Jerusalem, territory seized by Israel in the 1967 Six-Day War that Palestinians view as the capital of a future state.

The quick American endorsement may lead some other countries to think twice about voting against Canada because it means going against U.S. wishes – and it might also offer Ottawa hope that Washington would lend a hand with a little diplomatic arm-twisting if the race appears close. In the horse-trading world of diplomatic voting at international organizations, that could be critical.

Qatar will have to muster the votes of 115 countries at a meeting this fall – a tall order – to relocate the ICAO's headquarters, which employs 534 people in Montreal. That requires the votes of 60 per cent of the ICAO's 191 members to move the agency from the city where it has been headquartered since 1947. Countries that host the headquarters of international organizations will likely be worried about a potential precedent.

Prime Minister Stephen Harper weighed in on the bid Friday, saying he has never heard any serious complaints about the Canadian site for the ICAO, and "there is absolutely no reasonable case for moving the centre out of Montreal."

A group of UN ambassadors from Arab countries who met in New York on April 23 to discuss Palestinian issues devoted a section of the agenda to countering Canada. Since then, Qatar has made its bid for the ICAO and some Arab countries are considering backing it because of Ottawa's Mideast stand.

Mr. Baird noted Friday that he has travelled the Middle East several times, including a visit to five countries in March and early April, where he was received by high-level figures – who, he insisted, made no mention of Canada's policy on Israel. "We stand up and do what's right, not what curries votes."

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In fact, he visited Qatar to meet the country's Emir and its Prime Minister – who, according to Mr. Baird's spokesman, Rick Roth, gave no warning of the ICAO bid.

Some of the other Arab nations to which Mr. Baird travelled most recently may offer the best hope for an early public endorsement of Canada from an Arab nation: the United Arab Emirates, with which Mr. Baird settled a trade spat, and Jordan, to which Canada has provided more than $25-million in new aid, and which relies heavily on U.S. assistance.

"I have talked to at least two Arab countries who are very positive and supportive about Montreal continuing with the headquarters," Mr. Baird said at a news conference in Montreal, refusing to name them. He said he had "great conversations" with governments from Latin America and Asia.

Mr. Baird and Quebec's International Relations Minister, Jean-François Lisée, said they will work to clear away "irritants" raised by some ICAO delegations, including the difficulties African diplomats have faced in obtaining visas to come to Canada, tuition-fee exemptions for the older children of diplomats and the relative scarcity of international flights from Dorval airport.

Mr. Baird hinted Ottawa might go beyond its current agreement to fund the ICAO headquarters. "If we can make that deal even better, we're prepared to do so, on any irritants … we're all prepared to look at what our governments can do to make a great bid even stronger," he said.