WASHINGTON  - A key US lawmaker threatened Wednesday to hold up a landmark US-India nuclear agreement unless nuclear supplier states adopt a provision terminating the deal if India conducted a nuclear test explosion. Howard Berman, chairman of the House of Representatives foreign affairs committee, said if the 45-nation Nuclear Suppliers Group (NSG) did not impose such a condition, the deal could not be approved before President George W Bush leaves office in January 2009. "Given the lateness in the Congressional session, it would be better to review these complex matters in the next Congress when they can receive a full and serious examination," the Democratic legislator said in a letter Wednesday to Secretary of State Condoleezza Rice. The US House and Senate will adjourn in late September ahead of the presidential and congressional elections two months later. Bush and Indian Prime Minister Manmohan Singh agreed to the nuclear deal in 2005, under which the United States will provide energy-starved India civilian nuclear fuel and technology. The Bush administration later this month apparently intends to seek an exemption for India on nuclear commerce guidelines from the NSG with "few or none of the conditions" contained in a special US law governing the deal, Berman said. A key condition under the law - the Henry J Hyde United States-India Peaceful Atomic Energy Cooperation Act of 2006 - "is the immediate termination of all nuclear commerce by NSG member states if India detonates a nuclear explosive device," he said. Any exemption of this provision for India "would be inconsistent with US law, place American firms at a severe competitive disadvantage, and undermine critical US nonproliferation objectives," he said. "It would also jeopardize congressional support for nuclear cooperation with India, this year and in the future," he warned. Daryl Kimball, executive director of the US Arms Control Association, said Berman's letter was "very useful and significant. "It shows that Congress is concerned that the Bush administration may be seeking an exemption for India that would allow NSG trade to continue if India conducts a nuclear test explosion," he said. Berman also indicated he was committed to a "full and serious examination" of the deal's operational agreement adopted by India and the United States last year that raised various questions in Congress, Kimball said. New Delhi says there is nothing in the operational pact - called the 123 agreement - which places an embargo on India's right to carry out a nuclear test. It has asserted that it believes the Hyde Act to be irrelevant. Prime Minister Singh has also rejected claims by Indian opposition leaders that the deal would block the country from holding future tests. Berman said even if NSC members achieved consensus and the Bush administration submitted full details of the deal to Congress immediately after it reconvened on September 8, there may not be sufficient time to fully consider all issues before the legislature's adjournment on September 26. "This would give other countries an unacceptable head-start in securing commercial nuclear contracts with the Indian Government, thus placing US firms at a competitive disadvantage," he said.