WASHINGTON - Unless the United States modernizes its inventory of nuclear weapons and develops a replacement warhead, the atomic arsenal's long-term safety and reliability will deteriorate, Defense Secretary Robert M. Gates warned Tuesday.
Gates also broke with the Bush administration by saying the United States "probably should" ratify the Comprehensive Test Ban Treaty, an international agreement prohibiting new testing of nuclear weapons.
His remarks, in an address to the Carnegie Endowment for International Peace, represented his most extensive comments on the nation's nuclear weapons program as well as his first statement in support of the test ban treaty. The pact was signed by the Clinton administration in 1996 but has not been ratified by the Senate, and President Bush opposes it.
The Senate rejected the treaty in 1999, but the next administration could resubmit it. Some experts believe that support could build in the Senate if the Pentagon establishes that it can build a new weapon without testing. Gates suggested Tuesday that a new replacement warhead could be developed without testing.
He said the current nuclear stockpile has been re-engineered to extend its life span, but such extensions cannot continue indefinitely. Without a modernization program, Gates said, the long-term outlook for the arsenal is "bleak."
"No one has designed a new nuclear weapon in the United States since the 1980s, and no one has built a new one since the early 1990s," he said. The older and less reliable the nuclear arsenal is, he added, the more difficult it will be to make sharp cuts in the U.S. stockpile and reduce the number of nuclear weapons.
"To be blunt," Gates said, "there is absolutely no way we can maintain a credible deterrent and reduce the number of weapons in our stockpile without resorting to testing our stockpile or pursuing a modernization program."
For the last two years, Congress has cut most funding for the Reliable Replacement Warhead program, including $89 million sought by the National Nuclear Security Administration to determine the cost of building a new warhead.
"Currently, the United States is the only declared nuclear power that is neither modernizing its nuclear arsenal nor has the capability to produce a new nuclear warhead," Gates said.
Supporters argue that building a new warhead would allow scientists to add modern security systems to the weapons and improve their safety.
But the Reliable Replacement Warhead program, a project of the departments of Defense and Energy, is controversial, in part because some lawmakers believe that stopping nuclear proliferation will be more difficult if the U.S. is seen as developing a new generation of weapons. Others see it as a back-door way to develop new nuclear capabilities and lower the threshold for using them -- arguments Gates rejected.
"Let me be clear: The program we propose is not about new nuclear capabilities -- suitcase bombs or bunker-busters or tactical nukes," he said. "It is about safety, security and reliability."
In the question-and-answer session after his speech, Gates was asked whether the U.S. should sign the Comprehensive Test Ban Treaty. "If there are adequate verification measures, we probably should," he said.
Sen. Barack Obama, the Democratic nominee for president, supports the test ban. His Republican opponent, Sen. John McCain, opposed the treaty in 1999 but has promised to take "another look" at it.
George Perkovich, the vice president for studies at the Carnegie Endowment for International Peace, said Gates' endorsement of the treaty was important.
"There isn't a high Republican officeholder who has said anything that clear on it," he said. "That is interesting and good. That opens a lot of doors."