WASHINGTON: Two decades after the US began to scale back its nuclear forces in the aftermath of the Cold War, a number of military strategists, scientists and congressional leaders are calling for a new generation of hydrogen bombs.

Warheads in the nation’s stockpile are an average of 27 years old, which raises serious concerns about their reliability, they say. Provocative nuclear threats by Russian President Vladimir Putin have added to the pressure to not only design new weapons, but conduct underground tests for the first time since 1992.

“We should get rid of our existing warheads and develop a new warhead we would test to detonation,” said John Hamre, deputy secretary of Defence in the Clinton administration and now president of the Centre for Strategic and International Studies. “We have the worst of all worlds: older weapons and large inventories that we are retaining because we are worried about their reliability.”

The incoming Republican-controlled Congress could be more open to exploring new weapons.

“It seems like common sense to me if you’re trying to keep an ageing machine alive that’s well past its design life, then you’re treading on thin ice,” said Rep. Mac Thornberry (R-Texas), chairman-elect of the House Armed Services Committee. “Not to mention, we’re spending more and more to keep these things going.”

Thornberry also offered support for renewed testing, saying, “You don’t know how a car performs unless you turn the key over. Why would we accept anything less from a weapon that provides the foundation for which all our national security is based on?”

Some of the key technocrats and scientists of the Cold War say the nation has become overly confident about its nuclear deterrence. The nuclear enterprise, they say, “is rusting its way to disarmament.”

“We should start from scratch,” said Don Hicks, who directed the Pentagon’s strategic weapons research during the Reagan administration. “We have so much enriched uranium and plutonium left from old weapons we could use it properly for a new generation of weapons.”

In the 25 years since the Cold War ended, the US has significantly retreated from the brinkmanship of the arms race, reducing its stockpile from a peak of 31,000 nuclear weapons in 1967 to its current level of 4,804 weapons. Russia has cut its stockpile to about the same size.

After the Soviet Union fell in 1991, the US agreed to an international moratorium on testing, though it never ratified the Comprehensive Nuclear-Test-Ban Treaty. Halting underground tests was seen as a crucial step toward full nuclear disarmament because it would put a high barrier against developing new weapons.

The US allowed much of its weapons complex to deteriorate, particularly production facilities, as cooperation with Russia flourished in the 1990s.

Today, the signs of decay are pervasive at the Pantex facility in Texas, where nuclear weapons are disassembled and repaired. Rat infestation has become so bad employees are afraid to bring their lunches to work.

“They literally have to keep their lunch bags on a shelf that’s head high so it won’t get eaten,” Thornberry said. “They find them on their computers, in the hallways. It’s a continual problem.”

The buildings at the Y-12 National Security Complex in Oak Ridge, Tenn., are so old that a concrete ceiling recently collapsed into a production area.

The Obama administration has a $60-billion (Dh220 billion) plan to modernise the energy department complex and update weapons, including a new type of warhead that cannibalises components from older weapons.

The device would combine an atomic trigger from one weapon with a thermonuclear assembly from another. Called the interoperable warhead, it would reduce the number of weapons designs from seven to five, on the hopes that it would save money.

The device, which has been derided as an atomic ‘Frankenbomb’, has prompted criticism from arms control factions. Advocates of a strong US nuclear posture are not big supporters, either.

“Mixing and mashing parts into configurations that have never been tested before is not a good idea, by any means,” said Kingston Reif, director for disarmament and threat reduction policy at the Arms Control Association. “It’s going to cost money that we don’t have for a mission that plays an increasingly limited role in US national security.”

Some of the nation’s top nuclear weapons scientists say a better option is to design new weapons better suited to current threats.

In many ways, the growing nuclear capability of China, coupled with the addition of North Korea, Pakistan and India to the status of nuclear powers, has made deterrence strategy more complicated than during the Cold War.

John S. Foster Jr., former director of Lawrence Livermore National Laboratory and chief of Pentagon research during the Cold War, said the labs should design, develop and build prototype weapons that may be needed by the military in the future, including a very low-yield nuclear weapon that could be used with precision delivery systems, an electromagnetic pulse weapon that could destroy an enemy’s communications systems and a penetrating weapon to destroy deeply buried targets.

“After more than two decades, the nuclear deterrent could be in worse shape than we want to believe,” Foster said. “We need to demonstrate the proficiency of our weapons labs and our strategic forces.”

Restarting design and production in the US, however, would requires billions of dollars to build new facilities, including a metallurgy plant in New Mexico for plutonium triggers and a uranium forge in Tennessee for thermonuclear assemblies.