The chief executive of Toshiba Corp.'s Westinghouse Electric said on Wednesday he expects to sign a deal in June to build six nuclear reactors in India after marathon negotiations that began more than a decade ago.

In January, Westinghouse CEO Daniel Roderick told Reuters he hoped to be able to sign the deal in March, in time for a visit to Washington by Prime Minister Narendra Modi to attend a nuclear security summit that starts Thursday. On Wednesday, Roderick said the target date was now June.

"It may take until, I'm going to say, early June, which is the next time that there's going to be a government-to-government meeting with India," Roderick told Reuters in Washington.

The deal would be the first nuclear commercial power project since the United States and India agreed in 2008 to cooperate in the civil nuclear arena.

"We have submitted everything that we need to India and they have reviewed it and they are in the process now of finalizing the paperwork," Roderick said.

He declined to say how much the deal would be worth, or the price per unit of electricity, but said India had judged Westinghouse to be a "competitive energy source provider" and this would allow the contract to go on to the next phase.

Roderick said Westinghouse was still working on details of the nuclear operator liability issue, but that progress had been made.

"We are certainly comfortable enough to go to the next step from where we are right now, and if India continues to deliver on its milestones for the insurance program, then that should satisfy what Westinghouse needs," he said.

India wants to dramatically increase its nuclear capacity to 63,000 megawatts (MW) by 2032, from 5,780 MW, as part of a broader push to move away from fossil fuels, cut greenhouse gas emissions and avoid the dangerous effects of climate change.

For decades, India was shut out of nuclear trade because of its weapons program. The 2008 agreement with the United States gave it access to foreign suppliers without giving up arms that are primarily meant as a deterrent against nuclear-armed China.

But hopes that U.S. reactor makers would get billions of dollars of new business evaporated after India adopted a law in 2010 giving the state-run operator Nuclear Power Corp. of India Ltd. (NPCIL) the right to seek damages from suppliers in the event of an accident.

Indian officials have since sought to assuage suppliers' concerns, including by setting up an insurance pool with a liability cap of 15 billion Indian rupees ($226.16 million).

Roderick said he had been working on the agreement since 2005 and it was the longest negotiation he had ever been involved in.

"Most of our teams have finished and we've got all the paperwork in, so the next thing we will be waiting for is just the government approvals to move to the signature phase," he said.