Ahead of the summit meeting on the sidelines of G-8 in Germany's Heiligendamm sea-coast resort, officials of the two countries will meet to discuss the nitty-gritty of the 123 Agreement which has got stuck because of differences on aspects like reprocessing right.
A number of new proposals have been made and these will be discussed by officials.
The proposals have come up as part of efforts to veer around the differences, particularly on the reprocessing right, that have prevented any breakthrough in the year-long negotiations on the 123 agreement.
Key negotiators of the two countries -- Foreign Secretary Shivshankar Menon and US Under Secretary of State for Political Affairs Nicholas Burns -- met in New Delhi last week but failed to conclude negotiations as differences persisted.
The two sides are looking for a political push at the highest level to break the impasse in talks, which could come at the brief meeting between Singh and Bush.
In the backdrop of Singh and Bush affirming their commitment to the July 18, 2005, agreement on civil nuclear cooperation and the March 2, 2006 Separation Plan, the two sides are hoping for an expression of intent coming at the end of the "pull aside" meeting of the two leaders.
The two countries are aiming at sorting out differences particularly on issues like reprocessing right, perpetuity of fuel supplies and continuance of the civil nuclear cooperation if India were to conduct an atomic test.
India has been insisting on having the right to reprocess spent nuclear fuel and is not ready to accept any legally binding clause in the agreement that could cap its strategic nuclear programme.
Under the US law, Washington will have the right to seek return of material and equipment in the event of India carrying out nuclear tests.
The US contention that Presidential waiver could be a way out of the binding under the American law doesn't find much favour on the Indian side which argues that future Presidents could overturn the waiver.
Both sides have maintained that while some progress has been made at the recent talks, there was still distance to cover.
Against this backdrop, officials are unwilling to raise expectations of any breakthrough at the Singh-Bush meeting.
The 123 agreement being negotiated will operationalise the July 18, 2005 civil nuclear deal, ending a 30-year nuclear freeze.
Both sides are in the process of exchanging formulations well aware that the final agreement has to secure the approval of the US Congress and the Indian Parliament.
The two leaders will also discuss the thorny issue of climate change. Bush has been saying that developing countries like India need to cut greenhouse gas emissions but New Delhi has been insisting that the developed world should share the responsibility of fighting the problem.