TORONTO (AP) _ Usually low-key in their dealings with Washington, Canadian diplomats are turning bellicose in their campaign against a new U.S. immigration law they say will create severe backlogs at border crossings.

Canadians would be forced to wait hours at the border whether they were embarking on a Florida vacation or a quick shopping trip to Buffalo, Canadian officials contended Tuesday.

The U.S. law, passed by Congress last year, would require all foreigners to fill out visa forms upon entering the United States, starting in September 1998. Currently, Canadians are exempt from visa requirements and most simply answer a few verbal questions before crossing the border.

Attempts to exempt Canadians from the new law have failed, and Canadian officials this week abandoned quiet diplomacy.

``Frankly we are alarmed, disappointed and just a little frustrated,'' Doug Waddell, deputy head of mission at the Canadian Embassy in Washington, said in a speech to U.S. businessmen.

Canadian officials say the law runs counter to numerous initiatives aimed at streamlining border formalities between the world's two largest trading partners.

Under the legislation, each visit to the United States by Canada's 29 million residents would require filling out a visa form. Canadian officials foresee huge traffic backups at such busy crossings as the Detroit-Windsor tunnel and the Rainbow Bridge at Niagara Falls.

``Imagine for a moment the lineups,'' Waddell said. ``Lineups which include both Canadians and Americans. Lineups that extend perhaps miles at already busy border crossing points.''

Foreign Minister Lloyd Axworthy said the controls would be ``a major sort of barrier to the almost millions of transactions that take place across the Canada-U.S. border.'' Canadians annually make 76 million visits to the United States, according to the latest statistics.

``It's something the United States better look at very carefully,'' Axworthy said.

Canadian Ambassador Raymond Chretien said he had been assured by some members of Congress that Canada would not be subject to the law. But the U.S. Immigration and Naturalization Service has thus far balked at allowing exceptions and plans to launch a test project soon at the Thousand Island bridge that links upstate New York to Ontario.

Waddell said there is no need for test.

``A herd of sheep headed northbound in the southbound lanes and south in the northbound lanes of Interstate 81 would produce the same result. Do we really need a pilot project? Can't we anticipate the chaos it will create?'' he said.

Sen. Spencer Abraham, R-Mich,. chairman of the Senate subcommittee on immigration, said he will fight for an amendment that would exempt Canada.

There is also support for an amendment in the House of Representatives, sponsored by Rep. John Laflace, a Democrat from Buffalo, N.Y.

``The legislation in Congress wasn't targeted at Canada generally,'' said Gary Luczak, a spokesman for Laflace. ``It was legislation attempting to put in some more effective border controls.''