The US on Friday said enough was not done to iron out issues in the proposed 123 agreement with India to operationalise civil nuclear cooperation, but some "progress" was made in the recent negotiations in New Delhi.

"The United States has done its part. We've met every commitment we said we would meet," Undersecretary of State Nicholas Burns told reporters in Washington emphasising, "Right now, I would say the ball is in India's court."

"We were hopeful that we would be able to make progress to close out all of the issues on the 123 (agreement) talks. Some progress was made but in our view, not enough," Burns said.

At the two-day talks in New Delhi earlier this week, the two sides had indicated narrowing down of some differences.

Both sides are trying to bridge gaps on issues like fuel supply assurances, reprocessing of spent fuel and future nuclear testing by India.

New Delhi has alleged that the Henry Hyde Act, passed by the US Congress in December 2006 to allow civil nuclear trade with India, "significantly deviates" from the understandings of July 18, 2005, and March 2006, which was unacceptable to it.

India has made it clear that it will accept no deviation from the understanding reached between the two sides in 2006.

New Delhi has already conveyed its concerns to Washington and handed over a draft text of the agreement suggesting the clauses it wants to be incorporated.