Estimates of the size of China's nuclear arsenal range from approximately 155 to 240 warheads. Beijing is projected to have as many as 75 long-range nuclear-capable missiles in addition to 120 intermediate- and medium-range missiles, the U.S. Defense Department said in a 2011 assessment of China's armed forces.

Comparatively, the United States possesses 1,790 fielded long-range nuclear warheads and 822 deployed ICBMs, submarine-launched ballistic missiles and nuclear bombers, according to figures compiled in September by the State Department. As of May 2010, the United States had declared a total nuclear arsenal of 5,113 active and reserve warheads.

Unlike the United States, China keeps its nuclear warheads separate from launch vehicles, according to an official Chinese military textbook.

The Obama administration has publicized the number and types of warheads held in the U.S. nuclear stockpile but Beijing argues that providing similar information would make its nuclear weapons more vulnerable to a potential disarming first strike by the United States.

"Beijing claims that it cannot talk about those things because it's essential to their strategy for [the United States] not to know," Kulacki told a Washington audience at a forum on improving U.S.-Chinese nuclear discussions.

However, the Obama administration is unsatisfied with that stance and argues that a no-first-use pledge would be small comfort in a moment of crisis when lives are at stake, he continued.

This distrust in turn is insulting to Chinese representatives at bilateral nuclear talks, which have been taking place at varying levels for years.

Beijing views the U.S. insistence on more transparency in nuclear stockpile numbers as an attempt to shift the focus away from China's urging that the United States declare a no-first-use policy, according to Kulacki, who has spent years encouraging and facilitating dialogues between U.S. and Chinese analysts on nuclear arms control issues.

In the October issue of Arms Control Today, Kulacki wrote, "it is difficult for Chinese analysts to appreciate why a country with overwhelming conventional military superiority is unable to make a basic confidence-building commitment that a much weaker China finds acceptable."

It was only this May that the first official senior-level strategic security talks were held between the two powers. Other meetings have been at the less formal levels.

One notable success of these informal discussions by U.S. and Chinese arms-control specialists was the 2006 agreement to write a bilingual glossary of nuclear-weapons terminology with mutually accepted definitions, Kulacki said.

Faced with an impasse on the no-first-use issue, the Obama administration is seeking to engage in nuclear discussions with the People's Liberation Army's Second Artillery rather than with the Chinese Defense Ministry, which is more of a "military-diplomacy place" and not a decision-making body, according Li Bin, a noted expert on nuclear-disarmament issues in China.