Mr Manmohan Singh, who will also attend the United Nations General Assembly in New York and an India-EU gathering in Marseille, expects to finalise at least one landmark atomic deal before returning on Oct 2.

In New York, he will meet world leaders including Pakistan's newly elected President Asif Ali Zardari and Chinese Premier Wen Jiabao, foreign secretary Shiv Shankar Menon said.

Mr Singh will then make a brief visit to Washington on Sept 25 when officials hope to sign a bilateral accord allowing India to buy nuclear power plants, technology and fuel.

It would mark a milestone in warming ties between the US and India, a former Soviet ally, said security analyst C. Uday Bhaskar.

New Delhi, which is critically short of energy to fuel its booming economy, is looking at investments worth billions of dollars in its power sector.

Signed by Mr George W. Bush and Mr Singh in July 2005, the pact is awaiting final approval from the US Congress.

Mr Lalit Mansingh, a former ambassador to Washington, noted that the US Congressional calendar was 'very tight' with the session slated to end on Sept 26 ahead of Nov 4 polls.

But the passage of the deal 'doesn't seem impossible,' he said, pointing to mounting internal pressure for an endorsement before Mr Singh's arrival in Washington.

New Delhi, which agreed to open some of its reactors for inspection, already has approvals to buy fuel and technology from the International Atomic Energy Agency and the Nuclear Suppliers Group (NSG) that controls global atomic trade.

Mr Mansingh said that, even if the US deal was not signed, a nuclear cooperation accord with France was likely to be completed in Paris on Sept 30.

The French pact, negotiated in Jan during the visit to New Delhi of President Nicolas Sarkozy, is ready for signature according to Indian and French ministers.

Mr Kanwal Sibal, a former ambassador to Paris, said France had been a 'solid supporter of a nuclear deal with India for 10 years now, long before others.' 'It was the first country to begin a strategic dialogue with India after our 1998 nuclear tests, in order to create diplomatic space in our favour,' he said.

Since the election of Mr Sarkozy last year, France has supported India 'even more robustly' on issues like a permanent seat at the UN Security Council, Mr Sibal said.

India has been denied access to civilian nuclear technology since it tested an atomic weapon in 1974 and refused to sign the nuclear Non-Proliferation Treaty.

Washington spearheaded efforts that resulted this month in the Vienna-based NSG lifting a global ban on trade with India.

Before returning home, Singh will also take part in the ninth India-EU Summit in Marseille aimed at shoring up ties with the 27-member grouping which is India's largest trading partner. -- AFP