LANSING, Mich. - President Barack Obama's approval of a proposed bridge linking Canada and the U.S. represents a major project milestone, Canadian Labour Minister Lisa Raitt said Friday.

The presidential permit — a requirement for all U.S. border crossing projects with other countries — means construction of a second bridge between Windsor, Ont., and Detroit can now proceed.

"It's a real significant step forward for everybody," Raitt said in Detroit.

"We now have all the necessary approvals in both countries to proceed with construction."

The Windsor-Detroit border is the busiest crossing point between the world's largest trading partners, and the existing, privately owned bridge is a major bottleneck.

The hope is the new publicly owned bridge over the Detroit River will relieve congestion, smoothing the flow of traffic that includes about 8,000 trucks crossing daily.

"This is one of Canada's national infrastructure priorities," Raitt said. "That's how big it is."

Construction could start in 2015 or 2016 and be finished by 2020, although the owner of the 83-year-old Ambassador Bridge, Manuel (Matty) Moroun has launched lawsuits challenging the $1-billion project.

Michigan voters have rejected efforts by Moroun to slow down or stop construction.

Last June, Prime Minister Stephen Harper and Michigan Gov. Rick Snyder announced a deal whereby Canada would pay for the bridge and be repaid in tolls collected in Detroit.

Snyder praised Washington's approval of the project.

"Getting Michigan-made products to more markets faster will enhance our economic competitiveness in the future and help our state create more jobs," Snyder said in a statement.

The U.S. State Department said the proposed crossing will "serve the national interest" and "advance our vital bilateral relationship with Canada."

In one lawsuit, Moroun claims a "perpetual and exclusive franchise right" to operate the Ambassador Bridge free of competition from another span.

He also questions the constitutionality of a 1972 law giving the State Department authority to approve international bridges.

Snyder has denounced Moroun's lawsuits as a delay tactic.

Raitt said work has proceeded since Harper and Snyder inked the deal — including in areas of design work and acquiring needed properties.

The new permit now allows for acquisition of properties in the U.S.

Canadian Consul General Roy Norton, who is based in Detroit, said he was "thrilled" the permit was granted, calling it the last major piece needed to move ahead.

The total cost of the bridge is estimated at about $3.5 billion, including work on freeway interchanges, customs plazas in both countries and infrastructure work.

_ With files from The Associated Press.

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