Pressing India to speed up the implementation of the India-United States nuclear agreement, three influential Senators on Wednesday said the negotiations with the International Atomic Energy Agency and the Nuclear Suppliers Group should be wound up by May, failing which, New Delhi will not get a similar deal again.

Senators Joseph Biden, John Kerry and Chuck Hagel, who met Prime Minister Manmohan Singh [Images] in New Delhi on Wedensday, said if the deal is not taken up in the US Congress by June and the process completed during the tenure of President George W Bush [Images], any new US administration will renegotiate the deal.

They talked about the possibility of Indo-US relations being affected if the deal does not go through, saying there could be misunderstandings in India and questions as to whether the failure was deliberate by the US Congress.

During the meeting, Dr Singh told them about the dilemma and difficulties of his government because of coalition but remained optimistic about concluding the deal, the Senators told a press conference.

"We are running out of time. The clock is running," said Biden, Chairman of the Senate Foreign Relations Committee, when asked what message they conveyed to Singh.

Biden said India will have to firm up the safeguards agreement with the IAEA and seek waiver from the 45-nation NSG before June to enable the US Congress to vote on it.

"If the deal is not before the Senate by early June, there will be little chance (of the deal going through)," he said, adding there would be practical problems as the Congress will have only 20 sittings during which issues related to US budget will dominate.

"In order to be able to have time (for the deal) to be passed in the Senate, we really probably have to receive it in May. So, I think, somewhere in the next weeks, the decision has got to happen," Kerry said.

"If it government sends it (deal) to us at the last minute and if we are not able to get it done, then it will be seen here in India as a rejection or lack of trust (by the US Congress). That will be a terrible shame," Biden said.

"If the deal does not get through, it will be very complicated. It will have an indirect impact on the Indo-US relationship. You will begin to question, 'the US does not trust us?'... the only worry is misunderstanding will flow," the Democrat Senator from Delaware said.

"Our only concern is that if the (Indian) government does not move in a timely fashion, those who do not value our relationship, will play mischief in future," he said.

Noting that Dr Singh was committed to the deal as it was incredibly important for the bilateral relations, he said, "the Prime Minister is still optimistic."

Hagel said if the deal is not ratified by the Congress during Bush's tenure, the next administration, whoever the President is, will renegotiate the agreement. "It will not be the same agreement," he said.

Pointing out that the US values India, Biden said it should be brought to the table of discussion on overhauling global non-proliferation system, which the Democrats want.

He said some other countries also approached the US for a similar deal but it was turned down as India is special and is a non-proliferator. "There are a number of senators who will not be sad or disappointed if the deal does not come through as they feel it is one-sided and favours India," Biden said.

"It is in India's interest (to move fast on the deal). It is India's decision," he added, indicating that it was not a pressure tactic but a statement of facts. He said if India sends the deal to the US at the last moment, it will not go through and it could be seen in India as a rejection.

"That will be a wrong message. We trust India. We trust Indians. We value very much India being brought to the nuclear table," Biden said.

"Our common interests go beyond the nuclear agreement. We need to be partners and stay engaged," Hagel said. The US views its relationship with India much beyond the civil nuclear agreement and Dr Singh emphasised the incredible importance of it, he said.

"We asked the Prime Minister whether or not this (deal) was over and he said 'no'," Biden said.

He said that Dr Singh still appeared optimistic about the nuclear deal and explained the difficulties faced by the government, within the country, regarding the agreement. The senators also held talks with National Security Advisor M K Narayanan and had a luncheon meeting with some Parliamentarians.