NEW DELHI: Prime Minister Manmohan Singh made a strong pitch for Indo-US nuclear deal, saying it is crucial for ending nuclear apartheid against India and hoped progress will be made in the months ahead on the agreement which has "run into some difficulties."

Maintaining that the deal will open up new possibilities of cooperation not only with the US but also with other nuclear powers like Russia and France, Singh said that without the agreement trade in dual technologies could not become a reality.

"This nuclear agreement that we signed with the US has run into some difficulties, but it protects our national interest, it protects our capacity to use the nuclear power to protect our strategic interests," he said addressing IFS probationers at his residence.

"At the same time, it opens up new opportunities for civilian cooperation and without that, I think, the trade in dual technologies - sensitive advanced technologies - cannot become a reality," he said. Later, US Ambassador David Mulford met the Prime Minister and is understood to have discussed the civil nuclear deal and other bilateral issues.

Mulford was with Singh for about 30 minutes, sources said. They are understood to have deliberated on the nuclear deal and the prospects of it being implemented. Other issues, including climate change, also figured in the discussions.

The US has been saying that the time is running out on the deal and India needs to act fast. At a book release function in New Delhi, External Affairs Minister Pranab Mukherjee talked in favour of the deal saying nuclear power offered the most potent means to ensure energy security.

"In my view, nuclear power appears to offer India the most potent means to realize its long-term energy security" he said. Talking to reporters, Mukherjee said "nuclear energy is an option and we shall have to go (for the deal)."

"Given the oil price scenario, we seriously need to consider how our energy basket may be expanded so as to meet the deficit in India's energy requirement" Mukherjee added.

Meanwhile BJP party leader Venkiah Naidu has blamed the Prime Minister for the lack of progress on the Indo-US nuclear deal and said the government should have evolved a political consensus before going ahead with it.

It is the Prime Minister and his party that is to be blamed for the present state of the Indo-US nuclear deal, he told reporters.

"The government went the opposite way. It first signed the deal and then sought to have a political consensus and is now seeking cooperation of the opposition" he added.