India's nuclear deal with the United States, already dogged by opposition at home, has provoked alarm in neighbouring China, but experts expect Beijing to swallow its complaints rather than risk a face-off with New Delhi.
The pact between New Delhi and Washington would offer India US fuel and reactors while allowing it to stay out of the nuclear Non-Proliferation Treaty, keep nuclear arms and protect its military atomic complex from international inspections.
Even if the agreement survives opposition from Indian leftists, who could break apart the coalition government, China's veto could kill it at an international level.
<b1>Indian newspapers have cited recent Chinese media comments to suggest that Beijing could scuttle the deal at the Nuclear Suppliers Group (NSG), a 45-nation club that works by consensus.
Washington will need to go to the NSG, which is supposed to discourage nuclear trade with countries outside full safeguards, to ask for special leeway for India.
Chinese state media and think-tanks have said the nuclear deal will bolster US efforts to "contain" China and undercut international rules to stop the spread of nuclear weapons.
"The nuclear cooperation between the US and India not only seriously damages the integrity and effectiveness of the non-proliferation regime, it exposes the United States' multiple standards in non-proliferation", the People's Daily, official voice of the ruling Communist Party, said last month.
US moves to draw New Delhi into a loose regional alliance of democratic countries such as Australia and Japan which pointedly excludes Beijing have magnified China's worries, said Zhang Li, an expert on South Asia at Sichuan University.
"China has been trying to judge the nature of the US-India nuclear agreement and that process hasn't ended," said Zhang.
"In the past couple of months, the problem has become more prominent because of the spread of this democracy alliance. This will affect China's judgement."
Beijing balancing act
However, experts said China was unlikely to stymie the nuclear deal and risk pushing Delhi closer to Washington -- just when Beijing is seeking to avoid a destabilising confrontation with its rising Asian neighbour and longtime rival.
"The United States has decided that using India to check and balance China is of more importance than non-proliferation, and that worries China," said Shen Dingli, a nuclear security expert at Fudan University in Shanghai.
<B2>"But China does not want to push India towards the United States. I don't think China will stand out to oppose the agreement; it doesn't want to offend the United States or India."
China's government has steered clear of detailed comment on the deal since Indian Prime Minister Manmohan Singh and US President George W Bush agreed to it in principle in July 2005.
Even in private, Beijing officials have been non-committal, said a diplomat who spoke on condition of anonymity.
"For China, the political costs of opposing it would be too high. It would drive a wedge between China and India," said Zhang. "But China may demand adjustments, even just to make a point about its concerns".
China and India have been trying to expand diplomatic and trade ties after decades of rivalry that included a brief war over disputed territory in 1962. Territorial disputes persist, as do mutual suspicions.
But popular support for diplomatic independence will deter any Indian government from following Washington closely, even if New Delhi gets the deal, several Chinese analysts said.
"The US wants to use India to contain China," said a recent analysis of the agreement published by the China Arms Control and Disarmament Association.
"But out of its own strategic interests, India is most unlikely to form an alliance with the US to contain China."
As it seeks to sway New Delhi, Beijing is instead likely to promote its own civilian nuclear technology. When President Hu Jintao visited India in November last year, he pitched for such cooperation.
But China is also likely to seek expanded nuclear cooperation with India's rival, Pakistan, where Beijing has already helped build an atomic reactor -- and it will be able to point to the US-India deal to counter any criticism, said Shen.
The United States has ruled out similar help to Pakistan which, like India, has not signed key non-proliferation treaties.
"When the US has its nuclear business with India, it will find it difficult to point fingers at others," said Shen.