The US has sought to defuse a row following comments made by its envoy in India over its relations with Iran.
US Ambassador David Mulford warned that a landmark deal giving India US nuclear technology could collapse if India does not back a UN motion against Iran.
The US State Department said Mr Mulford was voicing his "personal opinion" and Mr Mulford says his remarks have been "taken out of context"
India has rejected attempts to tie its stance on Iran to the deal with the US.
The US is pursuing action against Iran which it suspects of trying to develop a nuclear weapons programme.
Washington agreed last year to share advanced civilian nuclear technology with Delhi, lifting sanctions triggered by India's nuclear tests in 1998.
State department spokesman Sean McCormark said that Mr Mulford was "reflecting" the "very strongly held feelings about Iran" in the Congress about the Iran issue.
"Ultimately, how India votes on this matter is going to be a decision of the Indian government. They voted to find Iran in non compliance the last time around and we certainly would encourage and hope that they vote for referral this time around," he said.
Mr McCormack also sought to delink the civilian nuclear deal with how India votes on the Iran issue.
"We deal with the Indian government on these two issues as separate issues. Certainly, they come up in the same conversations," he told reporters in Washington.
Correspondents say Mr McCormack's comments are a move to defuse any potential political and diplomatic row that could erupt between the two countries ahead of President George Bush's visit to India in March.
Mr Mulford told the Press Trust of India news agency in an interview that US keen to have India's support when UN atomic watchdog, the International Atomic Energy Agency, meets to discuss Iran.
"India has arrived on the world stage and is a very, very important player in the world," he said.
"And if it opposes Iran having nuclear weapons, we think they should record it in the vote."
India's failure to do so, he said, would have a "devastating" effect on US Congress members who have yet to approve the nuclear deal.
"I think the initiative will die in the Congress. Not because the administration would want it to, but the Congress will... so I think this is part of the calculation that India has to keep in mind," Mr Mulford said.
Mr Mulford also said the US had doubts about Indian ideas on the clear separation of its civilian and military nuclear programmes - a key condition of the technology-sharing deal agreed last year - did not meet the "test of credibility".
India reacted sharply saying that its agreement with the US on "civil nuclear energy co-operation... stands on its own merits".
One the key allies of the ruling Congress party-led coalition, the Communist Party of India (Marxist) has also demanded the government must clarify its stand after Mr Mulford's comments.
"These remarks raises serious apprehensions regarding the nuclear cooperation deal being negotiated with the US," the CPI(M) said in a statement.
Mr Mulford, however, issued a statement saying that his comments to the Press Trust Of India had "been taken out of context".
"Iran is a matter where we know India will vote on the basis of its own national interest," he said.
The Press Trust of India is standing by its interview with the ambassador.