Tarter and others said the administration had not decided to resume testing. Nevertheless, the review is likely to add to fears that President Bush might end the testing moratorium and push for developing "low yield" nuclear warheads that some weapons scientists and conservative lawmakers advocate.
Bush has said he has no plans to end the moratorium.
But Vice President Cheney and Defense Secretary Donald H. Rumsfeld have argued that the safety and potency of the U.S. arsenal can be assured only by periodically detonating randomly selected warheads underground.
"This is all part of a well-coordinated effort inside and outside the government to basically resume production of nuclear weapons," charged Stephen Schwartz, publisher of the Chicago-based Bulletin of the Atomic Scientists, an arms-control journal. "If you are going to do that, you are going to need to test, and this is what this exercise is all about."
Schwartz said the readiness review of the Nevada Test Site could provide "cover to China and Russia, and maybe even India and Pakistan," to begin preparing to resume their own nuclear tests if the United States abandons its self-imposed moratorium on testing.
Tarter dismissed such concerns.
"Understanding the state of readiness, I think, is a nonprovocative activity," he said.
The study of test-site readiness comes as the Pentagon conducts a separate review of U.S. nuclear strategy and forces ordered by Bush.
The issues being examined include radical cuts in America's nuclear arsenal and the future of the moratorium.
Bush supported the Senate's 1999 rejection of the Comprehensive Test Ban Treaty, saying a permanent global ban on nuclear testing would be unverifiable. His refusal to call for a new Senate vote on the treaty provoked a diplomatic protest by the European Union.
Britain, France and Russia are among 76 nations that have ratified the 1996 treaty. Like the United States, China has signed but not ratified the pact, and is observing a test moratorium.
Many experts say that returning to underground tests is unnecessary and could undermine the international nuclear arms-control system and provoke a new nuclear-arms race.
These experts contend that the United States can continue to rely on the so-called Stockpile Stewardship Program to ensure that its estimated 10,500 warheads remain defect-free. The program uses experiments, computer simulations, warhead inspections, and tests of non-nuclear components.
The Nevada Test Site is spread across 1,350 square miles of desert northwest of Las Vegas.
The main U.S. nuclear proving ground, it conducted 100 atmospheric and 828 underground tests between 1951 and 1992. It still conducts "subcritical" tests of nuclear components.
Tarter said the examination of the site's readiness to resume full-scale tests involves experts from the site, the Livermore and Los Alamos national laboratories, and a commission Congress appointed in 1999 to examine the nation's ability to maintain safe and reliable nuclear warheads without test explosions.
In a Feb. 1 report, the commission expressed concern about insufficient funding, crumbling infrastructure, low morale and other problems at the nuclear laboratories, nuclear weapons-production plants, and the Nevada Test Site.
The panel, headed by John S. Foster Jr., a former weapons designer, found it would take the test site 12 to 36 months to prepare a test.
"It is the panel's view that such lead times are unacceptable," the report said. "It seems prudent to take cost-effective steps to reduce lead times for testing to give future presidents a practical set of options for sustaining confidence in the stockpile."
Jonathan Landay's e-mail address is firstname.lastname@example.org.