A new $5-billion bridge is being planned for the Windsor, Ont.-Detroit corridor, sources told Radio-Canada.

Governments in Canada and the United States will work together to build a second bridge beside the overburdened Ambassador Bridge, say the sources.

An official announcement is expected in July.

A site has already been picked for the Canadian side of the bridge, Radio-Canada reported.

Canada and the U.S. risk losing as much as $28.6 billion US a year in trade by 2030 unless a second bridge is built, a joint governmental task force studying the need for a new crossing reported in 2004, citing daily traffic snarls on the Ambassador.

About 25 per cent of the trade between the two countries goes through the Windsor-Detroit trade corridor, with about 10,000 trucks travelling across the Ambassador each weekday. A highway tunnel also connects the two cities.

Prime Minister Stephen Harper is said to be pushing to have the deal finalized by the fall, before U.S. President George W. Bush departs from office in early 2009.

The French-language network of the CBC said the project, which is expected to create up to 25,000 jobs, would be the biggest joint construction effort in the history of Canada-U.S. relations, and the largest public-private partnership in Canadian history.

"For all of those governments to come together and say this is the plan — this is many, many years in the making," the CBC's Susan Pedler reported from Windsor on Thursday.

She said that for such a plan to take shape requires co-operation between multiple layers of government on both sides of the border, including municipal, provincial, state and federal bodies.

With files from the Canadian Press