Washington is backing China's long-standing application for membership in the Nuclear Suppliers Group (NSG), the cooperative association of countries aimed at controlling the export of nuclear materials, equipment and technology.
China's membership may be approved later this month by the NSC, whose 40 members now include the United States, Russia, France, Germany, Russia and Britain, officials said.
John Wolf, the assistant secretary in the US State Department's bureau of nonproliferation, told a congressional hearing Tuesday that China should be included in the NSG, where major nuclear export control issues were discussed.
"China as a nuclear supplier should face those issues head-on. That is one of the global responsibilities it should take on," Wolf told the international relations panel of the House of Representatives.
But some groups believe China could follow in the footsteps of Russia, which had posed difficulties in the NSG in the past, probably driven in part by Moscow's interest in protecting its nuclear supply relationship with India.
Wolf dismissed such a possibility, saying that China had stated that it would inform the NSG of particulars about its supply of a second nuclear reactor to Pakistan, for which an agreement was signed just earlier this month.
The first and second nuclear reactors are at Chashma, some 270 kilometers (167 miles) south of Pakistan's capital Islamabad.
Some lawmakers referred to Chashma II and expressed concern that the NSG would be saddled with a proliferation threat if Pakistan misused the Chinese technology.
Wolf said Washington knew for some time that China planned to supply Chasma
"But, although we would prefer that no such cooperation occur, Chasma II will be under IAEA (International Atomic Energy Agency) safeguards and the NSG full-scope safeguards provisions have always made allowance for the completion of agreements and contracts entered into before membership," he explained.
Henry Hyde, the Republican chairman of the House's international relations panel, warned that Pakistan's "record regarding non proliferation is unparalleled in its recklessness."
He also questioned China's cooperation so far in preventing Iran from acquiring nuclear weapons in the light of its former assistance to Tehran for precisely that purpose.
Democratic representative Tom Lantos said Congress must know whether China had committed to further toughening of international controls on the export of nuclear technology or likely to stall and delay further improvements to the regime.
"China, in joining the NSG with a contract in hand to provide a new nuclear power reactor to Pakistan, is a very serious issue," he said.
Since Pakistan does not allow international inspection of all its nuclear activities, NSG members are forbidden to engage in new nuclear cooperation with Pakistan, he said.
China's Pakistan contract however would be exempt from that prohibition, he added.
The architect of Pakistan's atomic weapons programme, Abdul Qadeer Khan, had publicly confessed to leaking nuclear secrets to Iran, Libya and North Korea.
Wolf told the legislators that tying China's NSG membership to a host of other issues at the last moment would not bring the United States progress on other issues.
Washington is banking on China to use its influence on North Korea to end its nuclear-ambitions.
Wolf also dismissed suggestions that Washington favored Beijing's membership because it wanted China to buy US nuclear power reactors.
But he said that if they bought from the United States "we would have substantial influence on how China manages its civilian nuclear programs in such areas as nuclear safety."