Secretary of the Interior Ken Salazar has announced an “emergency” six-month extension of a two-year ban on new uranium mine development near the Grand Canyon. The extra time, he said, was needed to finish an environmental impact statement on the potential effects of such mining on federal lands around the canyon.

Extension of the ban blocks the opening of 1 million acres of public and National Forest System lands surrounding the Grand Canyon to new uranium mining claims. The final environmental impact statement, Secretary Salazar also said, would now focus on a "preferred alternative" of a 20-year mineral withdrawal on those same lands.

"This alternative, if selected," he said, "would ensure that all public lands adjacent to the Grand Canyon National Park are protected from new hard rock mining claims, all of which are in the watershed of the Grand Canyon."

The secretary’s announcement, made Monday against the iconic backdrop of the Grand Canyon, was hailed by environmental and tourism advocates, but slammed by business groups who called the decision arbitrary and said billions of dollars were at stake.

Salazar argued that billions of tourism dollars were at stake if scenic vistas were spoiled or water resources tainted by mining on an unprecedented scale in the area.

Mining companies – including many international firms – in recent years staked more than 10,000 claims for future uranium mines near the mile-deep canyon as prices for the mineral used as fuel in nuclear power plants soared.

Most of those claims, however, have seen little or no development and have not yet been determined by the government to have "valid and existing rights" – a legal designation indicating that they must be allowed to proceed toward development under the requirements of the 1872 Mining Law. If the long-term ban takes effect, it would block most nascent claims from proceeding.

The draft environmental impact statement, a two-year process involving the Bureau of Land Management, examined the possible impact of no ban on mining, as well as other scenarios, including a ban on as many as 1 million acres. It was accompanied by nearly 300,000 public comments. Both the draft study and the comments influenced Salazar's decision to select as the preferred alternative a ban on mining across the entire area, he said.

Conservationists and environmentalists who had battled in court and in Congress for years to prevent mine development were thrilled by the decision.

"We're very pleased and thankful that Secretary Salazar has decided to use his authority to protect the Grand Canyon watersheds from uranium mining," Roger Clark, air and energy program director of the Grand Canyon Trust, said in an interview.

On the flip side, the American Clean Energy Resources Trust, a pro-uranium mining advocacy group, features this banner on its website: "Stop the Whining. Start the Mining."

"The secretary took $30 billion of American economic wealth and jobs off the table with his action today," Bob Weidner, director of government affairs for the group, said in an interview.

Monday's decision, Salazar noted, would not block at least some uranium mines from being developed in the area – claims that currently have valid and existing rights. There could be eight to 11 mines developed in the area, he estimated. Yet those, too, may face legal action by conservation groups.

"We adamantly disagree with the Bureau of Land Management's estimates," Mr. Clark says. "We don't believe that these claims have valid and existing rights."

Monday's decision could set a precedent for thousands of other mining claims now burgeoning along the borders of other national parks and wild lands. In April, at least 10 national "treasures" in the West – including the Grand Canyon – were rated as "at risk" from mining, according to a report by the Pew Environment Group, environmental watchdog based in Washington, D.C.