The Clinton administration is moving to place nearly 1 million new acres of land in the West under federal protection as national monuments, less than a month after Republicans in Congress failed in an attempt to wrest that authority from the White House.

The proposed sites are in Arizona and Idaho, whose congressional delegations are among the strongest opponents of the president's use of this power. The monument designation precludes commercial development or sale of a property to preserve it in perpetuity for its historic or scientific value.

Interior Secretary Bruce Babbitt is recommending that 293,000 acres in northern Arizona be added to create a Vermilion Cliffs National Monument, and that Idaho's Craters of the Moon National Monument be expanded from 54,440 acres to 720,400 acres, or about 14 times its original size, according to a department spokesman.

"The president has acted on these recommendations in as little as two weeks," Interior Department spokesman John Wright said Monday. "He can go on doing this right up to the moment the next president is sworn in."

Administration sources said Clinton intends to place many other large tracts of land under national-monument protection before leaving office. Thus far in his two-term tenure, Clinton has designated national monuments to set aside some 4 million acres, the most land within the lower 48 states to be given this protection by any president.

Republican Presidents Richard Nixon, Ronald Reagan and George Bush added no land to the national monument holdings.

The president is empowered to declare sites national monuments solely on his own authority under the 1906 Antiquities Act, which was first used by Theodore Roosevelt.

Last month, a Republican attempt to strip the presidency of monument-designation power was narrowly defeated in a largely party-line Senate vote of 50-49, with Illinois Sen. Peter Fitzgerald among six GOP defectors.

Western lawmakers in particular have asked that federal lands be open to mining, grazing, timbering and other "mixed uses," and they have characterized the president's designation authority as a dictatorial power.

The failed Republican measure would have turned that power over to Congress, where senators and representatives from the West would have better opportunity to obstruct the designations.

"This president is engaging in the biggest land grab since the invasion of Poland," complained Rep. Helen Chenoweth-Hage (R-Idaho), a longtime critic of federal conservation programs.

Under the designation proposed by Babbitt, the Craters of the Moon site in Idaho would be expanded to the south to encompass virtually the entire field of craters and lava flows that gave the weird, otherworldly landscape its name.

The original 54,440-acre section, set aside by President Calvin Coolidge in 1924, would continue under the control of the federal Bureau of Land Management. The additional 661,000 acres would be operated by the National Park Service as a conservation project and tourist attraction.

The 293,000-acre Arizona site is near the Grand Canyon and embraces the Paria Plateau and the Vermilion Cliffs, ranging from 3,100-feet to 7,100-feet high. The area is rich in Anasazi Indian artifacts predating European exploration of North America.

"Both of these recommendations cover unique, spectacular landscapes," Babbitt said. "So far, they have been untouched by development or sprawl, but the West is expanding rapidly, and this is the time to act."

Dave Simon, Southwest regional director of the National Parks Conservation Association, said in Santa Fe that his watchdog group welcomed the Vermilion and Crater designations, but added there are other areas in Arizona with a greater need for monument protection.

One is a 100,000-acre site adjoining Petrified Forest National Park that is increasingly endangered by real estate development, he said. Another is a 20,000-acre section outside Flagstaff that contains remnants of the northernmost settlement of the advanced Indian civilizations that once inhabited Mexico.

There are also some 3 million acres of Arizona's Sonoran Desert--one of only four major deserts in the U.S.--deserving protection, he said.

"We hope the Clinton administration will consider these too," Simon said.