A proposal to develop a copper mine near the southern edge of the Tonto National Forest has the support of Pinal County.

The county's Board of Supervisors voted unanimously this week in support of a resolution to urge Congress to recognize the Resolution Copper Mining Co. for its efforts to develop the mine near Superior.

The resolution comes as a House subcommittee prepares to hold a hearing next week on several mining bills, including one that would allow for a land exchange between the mining company and the federal government. The swap would allow the company to begin obtaining permits.

Members of Arizona's congressional delegation have said that the project could spur the creation of more than 3,700 jobs and generate billions of dollars in economic activity and tax revenue.

County supervisors said support for the project appears to be growing.

"This project is of vital importance to the county, the state and the nation," District 4 Supervisor and Vice Chairman Anthony Smith said. "We need to embrace this project - 52 percent of Pinal County people leave this county to go to work. We need to stop that."

Under a proposal pending since 2005, Resolution Copper Mining would swap 5,300 acres of land for conservation purposes for 2,400 acres of national forest land.

Opposition by conservationists and some American Indian groups has helped stall the exchange.

Opponents include the Obama administration and many Democratic lawmakers. They have argued that an environmental review should be completed before the exchange is made.

During debate in the House last fall, Democrats complained that the mining company would not have to pay royalties to the U.S. government for lucrative mineral rights that could be worth billions of dollars.

They also said the proposed mine site contains sacred Native American artifacts and important cultural areas that would be displaced by the mine.

One of the largest undeveloped copper resources in the world rests under the forest land in question. Company plans call for investing more than $6 billion in the proposed mine, which would be the largest copper mine in North America.