Linton F. Brooks, administrator of the National Nuclear Security Administration, discusses Nevada Test Site programs Tuesday at the administration's North Las Vegas office. Photo by John Gurzinski.

The resumption of full-scale nuclear weapons testing at the Nevada Test Site is not on the horizon, the nation's nuclear security chief said Tuesday.

But, Linton F. Brooks, administrator of the National Nuclear Security Administration, said the Bush administration intends to retain the option of conducting full-scale tests below ground at the test site, 65 miles northwest of Las Vegas.

"The reason this administration has been unwilling to push for the ratification (of the Comprehensive Test Ban Treaty) is that we don't want to close the door," Brooks said on a visit to the NNSA's Nevada Site Office in North Las Vegas.

"We have absolutely no evidence that we're going to need to test. ... We don't see any specific reason now that leads us to believe we'll need a test. On the other hand, we don't know everything about the future," Brooks said.

In Brooks' view, only a major problem with the nuclear weapons stockpile would prompt full-scale testing to resume at the Nevada Test Site, where the program was put on hold indefinitely in 1992, he said.

"It's pretty unlikely that you're going to see the return to testing," Brooks said. "And you're certainly not going to see a return to testing for developing new weapons. ... It's very hard to see a future in which that would be either necessary or wise or politically possible."

From 1951 through 1992, government scientists conducted 928 full-scale nuclear tests at the Nevada Test Site, including 100 above ground.

As for the possibility of developing new weapons using science-based techniques, such as laser fusion and subcritical experiments that detonate small amounts of nuclear materials, and analyzing the data with supercomputers, Brooks said: "Well, we don't know yet because we don't have any requirements from the Department of Defense to development new weapons.

"Even if we did, there's great concern by many in Congress about new weapons," he said. "I think that at the moment our focus is much more on making sure that we can modify" existing weapons components.

Brooks said by 2012, the United States will have 1,700 to 2,200 deployed nuclear weapons and "a fairly large number of non-deployed weapons."

"One of the reasons we keep a fairly large number of non-deployed weapons now," he said, "is a hedge both against geopolitics -- a new arms race with a new peer competitor -- and as a hedge against technical problems. You keep two different warheads for ICBMs (Intercontinental Ballistic Missiles) so that if one of them doesn't work you can upload the rest."

Brooks said scientists at national laboratories within the administration, a branch of the Department of Energy, keep a watchful eye on foreign nuclear capabilities by working with the U.S. intelligence community.

"The United States, I think, pays a huge amount of attention to Iran. I think there is widespread consensus that the Iranian program makes no sense unless you assume that one of the things they're after is a weapons capability."

Brooks cautioned that he doesn't want "to overstate the problem. There is no Iranian weapon now, I'm almost positive, and don't think there can be one for a while.

"But the reason the period we're at right now is so crucial is that what Iran is doing will give them knowledge and technical ability," he said. "Now is the time the international community needs to deal with this problem because I do think that the long-term prospects of an Iranian weapon are not in the interest of U.S. security."