China's nuclear posture is "an important contribution" to international disarmament and non-proliferation efforts, a former senior U.S. official said.

"China has decided that reasonably low levels compared with U.S. and Russia of nuclear weapons and delivery vehicles make sense for it ... This is an important decision on the part of China and would help in moving in the direction toward zero (nuclear weapons)," Thomas Pickering, former Under Secretary of State for Political Affairs, told Xinhua in a recent interview.

China has been firmly committed to a nuclear strategy of self-defense, adhered to the policy of no-first-use of nuclear weapons at any time and under any circumstances, and made a commitment to unconditionally not use or threaten to use nuclear weapons against non-nuclear-weapon states or nuclear-weapon-free zones.

Pickering suggested China play an active role in the process toward a nuclear-free world, given its status as a major nuclear state and a permanent member of the United Nations Security Council.

"You can't expect China to enter the process part way down with the whole process all worked out in advance without China's participation," said Pickering, who is also a leader of Global Zero, an international initiative to promote the elimination of nuclear weapons.

Chinese President Hu Jintao will attend the Nuclear Security Summit on April 12-13. More than 40 heads of state will gather in Washington to discuss how to safeguard their nuclear materials and keep them from falling into the hands of terrorists.

Labeling nuclear terrorism "a serious threat," Pickering said even though nuclear weapons are not easy to make because producing the materials requires a significant amount of production structure, people are still very concerned that terrorists might steal the material for nuclear weapons, and thus be able to make weapons or create weapons that wouldn't function as nuclear weapons but would spread radioactivity.

Despite the expected strong consensus on the importance of nuclear security, differences still remain.

"Some people may not feel the threat is very strong because they believe terrorists would not attack them. So that may distinguish between countries," he said, adding that different levels of urgency lead to different levels of commitment.

On the other hand, considering the high sensitivity of nuclear materials, states may not be willing to compromise some of their sovereignty to meet the new international nuclear security standards proposed by U.S. President Barack Obama in his landmark speech last April in Prague, capital of the Czech Republic.

"The summit itself is not likely to be a place to negotiate treaties, but it could in fact create a consensus among states which will pave the way for treaties and agreements that would follow," Pickering said.

The former U.S. ambassador to Russia also said the Global Zero movement has gained momentum since it was launched in December 2008.

"Over the last few years, we have come from a time when almost no one seemed to be interested in a world without nuclear weapons to the point where now presidents of the two major countries with respect to holding nuclear weapons have endorsed it," he said, referring to the new START treaty between the United States and Russia.

Obama and his Russian counterpart Dmitry Medvedev signed a successor treaty to the expired Strategic Arms Reduction Treaty (START) on Thursday, shrinking both nations' arsenals of strategic nuclear warheads to 1,550 over seven years, about a third less than currently permitted.

However, Pickering said the U.S.-Russian arms reduction is far from enough. "Other countries would not become involved until the number of weapons was reduced further between the U.S. and Russia."

In February, Global Zero rolled out an action plan on how to get to zero nuclear weapons, under which the United States and Russia should reduce their nuclear warheads to 1,000 each before other nuclear weapons states can be involved in the disarmament process.

"Against some time deadline, there are timelines, and while those are not rigid, they do give an indication of how one could move in that direction," he said.

However, further arms reduction negotiations between the two nuclear powers could be confronted with even greater challenges than in negotiating the just concluded treaty.

The Russians would like the United States to take all its tactical weapons out of Europe, but they don't seem to want to reduce the tactical nuclear weapons that they have right next to Europe in Russia, Pickering said.

Meanwhile, the United States seems to be reluctant to negotiate on its deployment of a missile defense system which it says is meant to defend against emerging threats such as Iran. Russia, however, sees it as an incursion into its sphere of influence.