The government announced an agreement Friday with a Canadian company that is the world's largest zinc producer on paying for a study of heavy-metal pollution in the Pacific Northwest's Columbia River.

Teck Cominco Ltd. of Vancouver, British Columbia, agreed to put up $20 million for assessing the impact of decades of upstream pollution in the river running from Canada into the U.S. The Environmental Protection Agency will monitor the study.

The agreement was reached after two years of negotiations that also encompassed suits by the state of Washington and the Colville Confederated Tribes of Eastern Washington.

The mining company had argued that the lawsuit should be thrown out because the United States could not impose rules on Canadian companies operating on Canadian soil.

But in 2004, U.S. District Judge Alan McDonald disagreed, saying U.S. environmental laws are intended to clean up pollution inside the United States, regardless of its origin.

EPA called the study an initial step toward launching a cleanup. It will assess risks from contamination to both people and the environment, and cover 150 river miles from the Canadian border downstream to the Grand Coulee Dam.

"We have moved from opposite sides of the table to sit down together as environmental problem solvers," Michael Bogert, EPA's regional administrator for the Northwest, said Friday. "The Bush administration is avoiding years of inefficient litigation and beginning the restoration of the river basin."

The lawsuit filed by the tribe and the state in 2004 was the first instance of Americans suing a Canadian company under the U.S. Superfund law. They accused the company of dumping millions of tons of heavy metals into the river for nearly 90 years, allowing it to flow into the United States.

They demanded the company comply with a December 2003 EPA order to pay for studies of pollution from a giant lead-zinc smelter in Trail, British Columbia, 10 miles north of the border. EPA officials said the 2003 order is being withdrawn as part of the settlement.

The Columbia runs through the tribe's reservation and provides fish for its members. About 15 miles south of the U.S.-Canada border, the river becomes Lake Roosevelt, the reservoir behind the Grand Coulee Dam.

EPA said it was the first time a settlement had been reached with a company over pollution that started in a foreign country and entered the United States.