By Fredrik Dahl,
* Western states question China over Pakistan nuclear plans
* Nuclear supplier states also discuss India at meeting
* Expert sees weakening of non-proliferation commitments
VIENNA, June 27 (Reuters) - Western states pressured China at closed-door talks last week to address concerns about its plans to expand a nuclear power plant in Pakistan and provide more information, but were rebuffed, two diplomatic sources said on Wednesday.
Beijing's atomic relations with Islamabad have caused unease in Washington, Delhi and other capitals due to Pakistan's history of spreading nuclear arms technology and fears about the integrity of international non proliferation rules.
"A number of countries asked questions and expressed concerns," said one official, speaking about the annual plenary session of the 46-nation Nuclear Suppliers Group (NSG), held on June 21-22 in the U.S. city of Seattle.
But China showed no sign of reconsidering its position on building two more reactors at the Chashma nuclear power complex in Pakistan's Punjab region, the official and another source said, a stance Beijing also took when the issue was raised in last year's NSG talks in the Dutch city of Noordwijk.
As its ties with the United States have suffered, Pakistan has been trying to move closer to Asian powerhouse China, which has welcomed Islamabad's overtures.
The two-day meeting also debated the issue of India's possible membership in the NSG, a consensus-based cartel that seeks to ensure nuclear exports are not used for military purposes by agreeing rules for such trade, the sources said.
In 2010, the United States announced backing for India's membership - a step that would make it the only country outside the nuclear Non Proliferation Treaty (NPT) in the group - but Pakistan has warned against allowing its rival to join.
"If India were to apply now, there would be quite a detailed discussion on non proliferation-related issues before a decision is taken," one of the sources said, suggesting there were differences of opinion within the NSG.
A statement by the U.S. National Nuclear Security Administration confirmed that the NSG's relationship with India was discussed, but did not mention the China-Pakistan issue.
"Participating governments called on all states to exercise vigilance and make best efforts to ensure that none of their exports of goods or technologies contribute to nuclear weapons programmes," it said on its website.
Close relations between China and Pakistan reflect a long-standing shared wariness of their common neighbour, India, and a desire to counter U.S. influence across the region.
Analysts say China agreed to expand Chashma to match a 2008 nuclear energy deal between India and the United States.
NUCLEAR PRINCIPLE EROSION?
Washington and other governments have said China should seek approval for the planned reactors from the NSG. But China argues that the construction of two additional units at Chashma was part of a bilateral deal sealed before it joined the NSG in 2004. China also supplied the facility's first two reactors.
European Union members of the NSG delivered a joint statement about the issue in Seattle, the two sources said. The U.S. delegation also "posed a question," one of them said.
"China basically reiterated that it comes under the grandfather clause," one source said, referring to Beijing's argument that the agreement was struck before it joined the nuclear suppliers' forum.
To receive nuclear exports, nations that are not one of the five officially recognised atomic weapons states must usually place their nuclear activities under the safeguards of the U.N. International Atomic Energy Agency, NSG rules say.
When the United States sealed a nuclear supply deal with India in 2008 that China and others found questionable because Delhi - like Islamabad - is outside the NPT, Washington won a waiver from that rule after contentious negotiations.
Pakistan wants a similar civilian nuclear agreement with the United States to help meet its growing energy needs.
But Washington is reluctant, largely because a Pakistani nuclear scientist, Abdul Qadeer Khan, admitted in 2004 to transferring nuclear secrets to North Korea, Iran and Iraq.
Pakistan tested nuclear devices in 1998, soon after India, and both nations refuse to join the NPT, which would oblige them to scrap nuclear weapons.
Nuclear analyst Mark Hibbs said there had been an erosion of the principle that recipients of nuclear exports must put all their atomic activities under IAEA safeguards.
"First by Russia a decade ago in its trade with India, then in the U.S.-sponsored India deal, and now by China's trade with Pakistan," Hibbs, of the Carnegie Endowment think-tank, said.
"Since the late 1990s we have seen a weakening of milestone non proliferation commitments by big powerful countries." (Editing by Andrew Osborn)