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

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

During the meeting, the Prime Minister 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 in New Delhi.

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

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