* $60 billion to be spent on new warheads over 25 years
* Effort will require new nuclear manufacturing complex
* Opponents say program sends wrong message to world
An Obama administration plan to spend $60 billion over the next 25 years to modernize the U.S. nuclear arsenal is misguided and violates the spirit of its pledge not to develop new nuclear arms, a Union of Concerned Scientists report said on Thursday.
The 81-page report by the independent nonprofit said the $60 billion for upgrading warheads is a fraction of what Washington plans to spend on its nuclear deterrent in the coming decades, on top of billions for new manufacturing facilities and billions more for delivery systems like submarines.
The spending comes despite President Barack Obama's endorsement of the goal of a world without nuclear weapons and his negotiation of the "New START" treaty with Russia, which committed the former Cold War rivals to reducing deployed strategic nuclear weapons to 1,550 each by 2018.
But Obama also has insisted that the United States must be confident that its remaining weapons will work as it attempts negotiate smaller and smaller nuclear arsenals with other atomic weapons states.
And he has come under pressure from Republicans to address the problems of the aging U.S. nuclear complex.
The Pentagon and the National Nuclear Security Administration, which is responsible for the maintenance and reliability of the arsenal, did not immediately respond to requests for comment on the report.
The United States produced its last nuclear weapon, based on 1970s technology, in 1990 and halted underground nuclear testing in 1992. Since then it has relied on computer simulation for testing and has refurbished older weapons to extend their life.
But concern about security and reliability has prompted the NNSA and the Pentagon to push for additional efforts to modernize the weapons. A plan released in June by the NNSA, which is part of the Department of Energy, calls for a new manufacturing complex to reconfigure and upgrade the arms.
MIX AND MATCH
The United States has seven warhead types. The new program would reduce the number of types and make some interchangeable on different weapons. There would be three warhead types for long-range missiles and two for bombs and cruise missiles.
"NNSA's plan violates the spirit if not the letter of the administration's pledge to not develop new nuclear weapons. It sends the wrong message to the rest of the world," said Philip Coyle, a researcher at the Center for Arms Control and Non-Proliferation who co-authored the report.
Lisbeth Gronlund, a co-director of UCS's Global Security Program who worked on the report, said in an interview that modernization efforts by NNSA could undermine confidence in the reliability of the arsenal.
Weapons in the U.S. arsenal have elements for a primary and secondary explosion. Under the new approach, Gronlund said, some primary and secondary elements would be mixed and matched, even though they may not have been physically tested together.
"People could well raise this as a concern and suggest we need to resume testing," she said. "So I don't see any reason to go down that road."
Gronlund said the idea behind moving to a smaller number of interchangeable warheads was that it would make it easier to reduce the size of the nuclear "hedge," the non-deployed warheads that are held in reserve.
The United States is thought to have as many as 2,650 non-deployed warheads, plus about 3,000 waiting to be dismantled, according to The Center for Arms Control and Non-Proliferation.
"The claim is that this (modernization) would allow them to eventually reduce the hedge," Gronlund said, but that would only be done after 25 years, which she described as "a little lame."
With the United States already cutting deployed warheads under New START, it is a "very realistic assumption" that Washington would reduce the number of non-deployed weapons over the next 25 years as well, she said.