India must complete by July all steps needed to conclude a nuclear technology deal with Washington to ensure the US Congress approves it before the presidential polls, three US senators said.

The India-US civilian nuclear energy deal has been held up due to stiff opposition from Prime Minister Manmohan Singh's Communist allies who prop up the minority Congress-led government.

"Time is of the essence," said Joseph Biden, one of three Democratic senators who were on a one-day visit to New Delhi after monitoring Pakistan's parliamentary elections earlier this week.

The pact still needs approval from the International Atomic Energy Agency to place India's civilian nuclear reactors under UN safeguards as well as from the 45-nation Nuclear Suppliers Group, which regulates global civilian nuclear trade.

The agreement, which would give New Delhi crucial access to civilian atomic technology, requires final approval by the US Congress where it currently enjoys bipartisan support.

But Washington officials say the deal is running out of time with a tight 2008 legislative calendar ahead of November's US presidential elections.

"If we don't have the deal back with us clearly prior to the month of July it will be very difficult to ratify the deal -- not on the merits (of the deal) but on the mechanics on which our system functions," Biden told a news conference.