The Indo-US nuclear deal is facing new difficulties which may prevent it taking effect this year, US officials and experts said on Tuesday.
Caught up with defence and homeland security issues, the US Congress may not give final approval to the agreement before ending its legislative session, leaving the deal's fate to a new Congress that will take office in 2007, they said.
Also, India has objected to key provisions, causing some US officials to question New Delhi's commitment.
The deal would allow India to buy American atomic fuel and reactors for the first time in 30 years, even though it has not signed the Nuclear Non-proliferation Treaty.
US Senate leaders plan to meet on Wednesday to discuss a possible timetable for action but the hurdles are considerable, sources said.
"It's unlikely to get done. We have limited legislative days left and much to do," an aide said.
Congress could adjourn as early as September 29, but there are plans for a "lame duck" session after the November election.
A senior US official said the administration still hopes the Senate will act. "There is strong bipartisan support for the legislation but their calendar is complicated," he said.
The nuclear agreement was announced by Prime Minister Manmohan Singh and George Bush in July 2005. It cannot take effect until the US Senate and the House of Representatives change US law banning nuclear cooperation with India and approve technical details in a separate cooperation agreement.
Also, the Nuclear Suppliers Group, an international body which controls nuclear exports, must change its rules and India must agree with the UN nuclear watchdog, the International Atomic Energy Agency (IAEA), on inspecting civilian nuclear facilities.
The House had overwhelmingly approved the nuclear deal in July. It requires the rising South Asian power to forgo future nuclear testing and cooperate with the United States in curbing nuclear exports.
The Senate has not acted partly because of a jammed work schedule. Congressional sources said despite Bush's rhetorical commitment, there is little sign he is expending political capital to win passage.