Describing the nuclear deal as a "landmark" in Indo-US relations, prime minister Manmohan Singh today said the two countries are finalising details to make the pact fully operational, a step that will remove restriction on the flow of nuclear technology and open a large area of commercial opportunity for American businesses.

India and the US will also put in place a framework for bilateral cooperation in energy, security and climate change tomorrow when the two sides sign an MoU in this field.

Addressing the US-India Business and Chamber of Commerce here, he also said that new avenue for Indo-US collaboration has been opened in the defence sector with India allowing up to 26% foreign investment in this sector.

"Our engagement with the US has been expanding on many fronts, throwing up new business opportunities," he said.

"The nuclear agreement was a landmark in Indo-US relations and I would like to acknowledge with deep appreciation, the very supportive role American business played in persuading Congress to support the initiative.

"We are currently finalising the details that will make the agreement fully operational. Once that is done, it will remove restrictions on the flow of technology in nuclear and many other areas. This will open a large area of commercial opportunities for US business," Singh said.