Tom Lantos, the top Democrat on the House of Representatives' powerful international relations committee scrutinizing the nuclear deal, expressed concern to visiting Indian Foreign Secretary Shyam Saran over New Delhi's training of the Iranian navy, the lawmaker's spokeswoman Lynne Weil told AFP.

"Congressman Lantos pointed out that episodes of conflict in relations between US and India, such as India's early wavering in its commitment to refer Iran to the UN Security Council and more recent concerns raised about Iranian troops receiving training from India will only undermine Congressional support for the deal," she said.

Reacting to the concerns, the Indian government said two Iranian naval ships with about 200 personnel were on a six-day "informal" visit to the southern Indian naval base in Kochi in March while on an annual sea training sortie in the Arabian Sea.

The port call was essentially "diplomatic-goodwill" and not part of any training package, said Venu Rajamony, spokesman for the Indian embassy in Washington.

He said the Iranian ships "interacted" with the Indian Navy as part of the visit, adding that activities included courtesy calls on Indian naval officers, navigational simulation and recreational activities such as yachting.

Lantos and Saran discussed the US-Indian nuclear agreement in the larger context of bilateral relations "which they agreed are blossoming in many respects," Weil said.

But Lantos noted that "at a time when gestures from allies are significant -- not symbolic gestures alone but substantive gestures -- the Indian government should look for opportunities to make gestures that underscore the strength of the bilateral friendship," she said.

The India-US nuclear deal gives energy-starved India access to long-denied civilian nuclear technology in return for placing a majority of its nuclear reactors under international inspection.

For it to be effective, the US Congress has to amend the US Atomic Energy Act, which currently prohibits nuclear sales to countries that are not signatories of the Non Proliferation Treaty (NPT).

US lawmakers are reportedly sceptical about giving their mandatory approval to the deal as India has refused to sign the NPT and has developed nuclear weapons on its own.

Washington meanwhile is trying to rein in Iran's uranium enrichment activities amid suspicion that Tehran could be pursuing covert development of nuclear weapons.

On Wednesday, the UN Security Council in New York unanimously voted to give Iran 30 days to fall into line with long-running calls to abandon uranium enrichment.

India is treading a tightrope as it tries to firm up the civilian nuclear deal with the United States and maintain its traditionally strong ties with neighbour Iran.

In February, India voted with 26 other nations to refer Iran to the UN Security Council amid charges by communists within the ruling Indian coalition that New Delhi's foreign policy was being dictated by Washington.

Saran warned Thursday of a setback in US-India ties if Congress refused to ratify the nuclear deal, clinched on March 2 by US President George W. Bush and Indian Prime Minister Manmohan Singh.

"If this particular agreement does not go through, there is no doubt there will be, in terms of the expectation that has been created, in terms of the enthusiasm that has been created, there will be some falling back," Saran said when fielding questions on the deal at a Washington forum.

Saran, the top civil servant in the Indian foreign ministry, said inevitably the public focus of the envisioned strategic partnership between the two nations had been on the nuclear deal even though bilateral relations covered many key areas.

"If this does not go through, it does not mean that everything else will fall by the wayside but at the same time we should also recognise that for good reason or bad, there is intense focus on this particular agreement," he said.

"Therefore whether we like it or not, this has become very symbolic of what we want to do with India-US relations," he said.