The United States said on Monday that it was carefully reviewing China's plans to build two civilian nuclear reactors in Pakistan, urging all nations to respect non-proliferation commitments.
The China National Nuclear Corporation has agreed to finance two more civilian reactors at the Chashma site in Pakistan, despite fears abroad about the safety of nuclear material in the Islamic nation.
China earlier built two reactors for Pakistan. But Beijing in 2004 entered the Nuclear Suppliers Group, a cartel of nuclear energy states that forbids exports to nations lacking strict safeguards by the International Atomic Energy Agency (IAEA).
US Deputy Secretary of State James Steinberg said that discussions were underway about the issue and the United States has not "reached a final conclusion."
"But it's something we're obviously looking at very carefully," Steinberg said in response to a question at a forum at the Brookings Institution.
"I think it's important to scrupulously honor these non-proliferation commitments," he said. "We'll want to continue to engage on the question, about whether this is permitted under the understandings of the IAEA."
Some analysts believe that China was emboldened to go ahead with the deal after the United States in 2008 signed a landmark nuclear agreement with Pakistan's arch-rival India.
India, like Pakistan, refuses to sign the nuclear Non-Proliferation Treaty. But former US president George W. Bush in reaching the deal praised India's track record on non-proliferation.
By contrast, the father of Pakistan's nuclear bomb, Abdul Qadeer Khan, confessed in 2004 to sending nuclear secrets to Iran, Libya and North Korea, although he later retracted his remarks.
Leaders of China, India and Pakistan all attended a major summit in Washington last month convened by President Barack Obama and pledged to work to preserve nuclear security.
Pakistan, a frontline state against Islamic extremism, has pressed the United States for a nuclear deal similar to India's. US officials have promised to listen but the deal is widely seen as a political non-starter in Washington.