The Indo-US nuclear deal that remained stalled due to domestic politics in India is almost certainly dead, a senior American official indicated, adding its collapse will be a "historic blunder" for India.

Asked whether it was now impossible to push the deal through in the dying days of Bush's term, Ashley Tellis told a British newspaper: "That is probably correct."

Tellis is one of the original architects of the historic deal and is now an adviser to John McCain's [Images] presidential campaign.

"Even if the Indian government were suddenly to turn around and get the IAEA stage completed, there will be no time for the remaining two stages," Tellis told the Financial Times.

The deal has been touted by US President George W. Bush as one of his signature foreign policy achievements.

Tellis's remarks came even as Prime Minister Manmohan Singh [Images] said he still continued to hope that "we will make progress in the months that lie ahead" after admitting that "our domestic politics has prevented us from going ahead".

After New Delhi secures the approval of the board of the International Atomic Energy Agency(IAEA), the deal would have to be cleared by the 45-member Nuclear Suppliers Group before returning to the US Congress for final approval.

The newspaper noted that US officials continued to hope that Singh would persuade his colleagues, including Congress president Sonia Gandhi [Images] to face down the Communist parties that last year threatened to pull the plug on the coalition government if it pushed ahead with the deal.

The newspaper said that senior Indian officials, who declined to comment, say privately that their best chances of reviving the deal would come with the election of John McCain, the Republican party's presumptive presidential candidate, who last month stated his strong support for it.