A top Indian defence official negotiating a $12 billion deal to buy France's Rafale fighter jets has died of a heart attack, further complicating talks over the delayed contract, officials said Thursday.

India chose France's Dassault Aviation in January 2012 for exclusive negotiations for 126 aircraft, but successive deadlines to complete one of the world's biggest defence contracts have slipped by.

Chances of Dassault meeting a target to conclude the huge and complicated production-sharing agreement this year are dwindling, with elections looming in the first half of next year.

Arun Kumar Bal, a joint secretary in the defence ministry in charge of air acquisitions, died Wednesday from a heart attack at the age of 52, meaning a replacement will now have to be named.

"We don't think his death will have any impact on the MMRCA," a defence ministry official, who asked not to be named, told AFP referring to the Medium Multi-Role Combat Aircraft deal.

"The ministry will just have to name a replacement," he added.

But a senior officer familiar with defence acquisitions said Bal was part of the "decision-making process" and in charge of examining Dassault's ability to meet the requirements stipulated by the government.

"It's a fact that Bal was associated with the programme for a while and so the new officiating person will need to familiarise themselves with his work," the officer said.

Defence Minister A.K. Antony, 73, is also currently in hospital where he is recovering from surgery on his prostate.

India is the world's biggest arms importer -- partly a consequence of its weak domestic production capacity -- and foreign defence companies are jostling for huge contracts for helicopters, planes and weaponry.

But as well as elections next year, the state's finances are strained with the government under pressure from investors and ratings agencies to keep the public deficit below its "red line" of 4.8 percent of gross domestic product.