QUEBEC - Prime Minister Stephen Harper says there is absolutely no reasonable case to move the International Civil Aviation Organization out of Montreal.

"It's been based in Montreal for a very long time," Harper told a news conference in Quebec City on Friday. "Montreal, Quebec, Canada have been very good hosts from everything I understand.

"I'm certainly not aware of any serious complaints about how we host the organization. Montreal's a sophisticated city that is a hub of the aerospace industry around the world.

"There is absolutely no reasonable case to move the centre out of Montreal."

His comments came shortly after Foreign Affairs Minister John Baird and Quebec cabinet minister Jean-Francois Lisee held a news conference in Montreal to announce a common front to prevent ICAO from moving to Qatar.

Baird said all the parties involved in the bid to keep ICAO in Montreal, including businesses and municipal politicians, are more united than ever.

Qatar made a pitch last month to the agency about moving its headquarters to the Middle East kingdom's capital of Doha. Baird was in Doha in early April and says Qatar officials didn't mention they were going to make any such bid.

"I want to assure you that the federal government understands what's at stake here," Baird said in Montreal.

"We are ready to work with the Quebec government, the City of Montreal, as well as air and aerospace companies to make sure that (ICAO) stays in Montreal."

ICAO sets international standards for civil aviation and is the only United Nations agency based in Canada.

Baird points out that Qatar is a country with great wealth and is offering a lot of money to lure the agency to Doha, but that shouldn't be a factor.

Also backing Canada's bid are international unions who say a move to Qatar is at odds with the ICAO's mandate.

"How can an organization that has to defend the rights and safety of workers and passengers be moved to a state whose citizens' pleas for democracy are answered with batons and buckshot?" David Cockroft, the general secretary of the International Transport Federation, said in a statement earlier this week.

Canada has played host to the ICAO since 1946. Its current headquarters were built in the 1990s at a cost of $100 million.

Losing the ICAO would be a financial and political blow for Canada.

Montreal is the hub of Canada's aviation industry, and its international reputation as a major player is reflected in the ICAO's longtime residency.

The organization also feeds the city's economy; it employs 534 staff and says it generates some $80 million annually for Montreal's economy and 1,200 direct and indirect jobs.

The Qatari bid, meanwhile, is seen by government critics as being politically motivated and a reflection of Canada's pro-Israel policy in the Middle East.

For the bid to prevail, a minimum of 60 per cent of the ICAO's 191 member states must sign off, a threshold that could send a strong rebuke to Canada.

A vote is set for September.