WASHINGTON — The Obama administration said Friday it would for the first time require companies drilling for oil and natural gas on public and Indian lands to publicly disclose chemicals used in hydraulic-fracturing operations.

The proposed rules on so-called fracking also set standards for proper construction of wells and wastewater disposal.

Interior Secretary Ken Salazar said the long-awaited rules would allow continued expansion of drilling while protecting public health and safety.

"As we continue to offer millions of acres of America's public lands for oil and gas development, it is critical that the public have full confidence that the right safety and environmental protections are in place," Salazar said.

The new rules, which have been under consideration for a year and a half, were softened after industry groups expressed strong concerns about an initial proposal leaked earlier this year. The proposal would allow companies to file disclosure reports after drilling operations are completed, rather than before they begin, as initially proposed. Industry groups said the earlier proposal could have caused lengthy delays.

Some environmental groups criticized the change as a cave-in to industry, however, Salazar said the rules were never intended to cause delays, only to ensure that the public is "fully aware of the chemicals that are being injected into the underground" by companies seeking to produce oil and natural gas.

The Bureau of Land Management, which oversees drilling on public lands, estimates that 90 percent of the approximately 3,400 wells on federal and Indian lands were drilled using hydraulic-fracturing techniques.

The rules would not affect drilling on private land, where the bulk of shale exploration is taking place. A nationwide drilling boom in formations such as the Marcellus Shale and the Bakken in North Dakota and Montana, as well as in traditional production states such as Texas, Oklahoma, and Louisiana, has led to 10-year lows in natural gas prices.

Still, Salazar said he hoped the new rules could be used as a model for state regulators.

"We hope our leadership is followed," he said at a news conference.

Industry groups and Republican lawmakers say federal rules are unnecessary, arguing that states already regulate hydraulic fracturing, in which water, sand, and chemicals are in injected underground to break up dense rock that holds oil and gas.

The industry also has complained that disclosure of chemicals used in fracking could violate trade secrets, although Salazar said the rule would include exemptions for specific formulas. Some of the chemicals used in fracking are benzene, toluene, ethylbenzene, and xylene, all of which in significant doses can cause health problems.