By Fredrik Dahl
VIENNA (Reuters) - China called on the United States and Russia - which hold the vast majority of the world's nuclear warheads - on Monday to make further "drastic" cuts in their atomic arsenals.
A senior Chinese diplomat also told a meeting in Vienna that the development of missile defense systems which "disrupt" the global strategic balance should be abandoned, a possible reference to U.S. plans in Europe that have angered Russia.
A new U.S.-Russian arms reduction treaty will cut long-range, strategic nuclear weapons deployed by the two Cold War-era foes to no more than 1,550 on each side within seven years after it came into force in February 2011.
But they still have by far the most nuclear arms - a fact stressed by the Chinese representative on the opening day of a two-week conference to discuss the Non-Proliferation Treaty (NPT), a 1970 pact to prevent the spread of atomic bombs.
China, Britain and France are the other three recognized nuclear weapons states. But the size of their arsenals are in the low hundreds, well below those of the United States and Russia which have thousands of nuclear warheads.
Ambassador Cheng Jingye, head of the Chinese delegation, said all nuclear weapons states should publicly undertake "not to seek permanent possession" of atomic bombs.
"As countries with (the) largest nuclear arsenals, U.S. and Russia should continue to make drastic reductions in their nuclear arsenals in a verifiable and irreversible manner," he said, according to a copy of his statement.
"Other nuclear weapon states, when conditions are ripe, should also join the multilateral negotiations on nuclear disarmament," Cheng added, apparently referring to the five recognized nuclear-armed countries.
India and Pakistan - which also have nuclear arms - are not part of the NPT. Israel, widely believed to have weapons arms, is also outside the treaty, as is North Korea, which is believed to be preparing for a third nuclear test.
The Non-Aligned Movement of developing and other states also called on the United States and Russia to cut their arsenals, expressing concern that nuclear weapon modernization undermines the "minimal reductions" agreed by them.
MISSILE SHIELD CONTROVERSY
China closely guards information about its nuclear arsenal. However, the U.S. Department of Defense has said that China has some 130-195 deployed nuclear-capable ballistic missiles.
The head of the U.S. delegation, Ambassador Susan Burk, earlier told delegates that her country was making progress on disarmament and it would "detail those efforts this week."
Shortly after taking office in 2009, U.S. President Barack Obama set the goal of eventually ridding the world of nuclear weapons as a central theme of his presidency and pledged dramatic steps to lead the way.
Obama unveiled a revamped policy in 2010 renouncing development of new nuclear weapons and restricting use of those already in the U.S. arsenal. He followed that up by signing the new START landmark arms reduction deal with Russia last year.
But momentum seems to have slowed on Obama's nuclear agenda and, with the November U.S. presidential election looming, chances for major new advances look doubtful.
Burk said The United States has made clear that it "understands its special responsibility to take concrete steps towards a world without nuclear weapons by pursuing nuclear disarmament."
France said it was one of few states to have taken "ambitious, irreversible" disarmament action in the past 15 years, and now had less than 300 nuclear warheads.
"In the last 15 years we have cut the number of nuclear warheads by half," added Ambassador Jean-Hugues Simon-Michel.
Britain - whose nuclear stockpile consists of fewer than 180 strategic warheads - is "fully committed to the long-term goal" of a world without nuclear weapons, said the UK representative.
But as long as large arsenals remain and the risk of proliferation continues, its "judgment is that only a credible nuclear capability can provide the necessary ultimate guarantee to our national security," Ambassador Jo Adamson added.
The development of missile defense systems "which disrupt global strategic balance and stability should be abandoned," Cheng said, without elaborating.
Washington says a planned European missile shield is meant to protect against a potential Iranian threat, but Russia says it risks tipping the balance of nuclear power between itself and the United States in Washington's favor.
(Editing by Ron Askew)