The Obama administration has extended for six months a 2009 moratorium on new uranium mining claims on one million acres around the Grand Canyon. This is good news; even better is the promise from Ken Salazar, the interior secretary, that he will soon recommend a 20-year ban on new claims in the region. That is the maximum allowed under the 1872 mining law.

With uranium prices rising, the number of mining claims have jumped sharply over the last few years. There have been about 3,500 claims in the Grand Canyon-area alone. If developed, they would generate toxic wastes that would threaten the Colorado River — the source of drinking water for roughly 27 million people — the aquifer and the Grand Canyon ecosystem in general.

Mr. Salazar said he could not cancel valid existing claims, but there is likely to be little actual mining. The decision to “withdraw” the land from future claims creates new regulatory hurdles for existing claimants, who must demonstrate, among other things, that they had discovered actual mineral deposits before the 2009 moratorium. Only a handful have been able to do so.

There have been the usual complaints from mining lobbyists and their Congressional allies. Representative Jeff Flake, a Republican from Arizona, has threatened to use the interior appropriations bill to block Mr. Salazar’s plan. The moratorium will have little effect on the country’s uranium supply, most of which comes from Wyoming and New Mexico.