CHRONOLOGY - Twists and turns in the India-U.S. nuclear deal

REUTERS - A historic nuclear energy deal between India and the United States is hanging in the balance due to political opposition in New Delhi but could still be saved if it reaches the U.S. Congress early next year, analysts said.

Communist allies of Prime Minister Manmohan Singh's coalition have demanded the deal be put on hold until their concerns are addressed and have implied they would end their support for the government, triggering fears for the pact.

Here is a timeline of some key developments over the past two years:

* July 2005: Prime Minister Singh and U.S. President George W. Bush agree in principle to a landmark civilian nuclear cooperation deal. The deal reverses 30 years of U.S. policy opposing nuclear cooperation with India because it developed nuclear weapons in contravention of global rules and never signed the Non-Proliferation Treaty, or NPT.

* March 2006: Bush pays a three-day visit to India during which the two countries agree on India's plan to separate its civilian and military nuclear reactors, a key requirement for the deal to go through.

* Dec. 2006: U.S. Congress overwhelmingly approves the deal. Three other approvals -- from the 45-nation Nuclear Suppliers Group, the International Atomic Energy Agency and a second time by the Congress -- are still needed before nuclear transfers to India can actually take place.

* Dec. 2006: Bush signs the law approved by Congress, which makes changes to the U.S. Atomic Energy Act. Analysts say the deal could be fully approved in roughly six months.

* July 2007: The two countries announce finalisation of the deal after months of tough negotiations on a bilateral pact. India had objected to what it said were new conditions in the agreement unacceptable to it.

* Aug. 3: Text of the bilateral pact, called the 123 agreement, is unveiled simultaneously in both countries. Indian analysts and nuclear experts say it meets most of New Delhi's demands.