Washington: India, which has drastically reduced its oil imports from Iran under US pressure, stands to gain from the historic accord reached between Tehran and six world powers to limit its nuclear program in return for lifting sanctions.

But before India, which imports 70 percent of its oil supply, turns back on the taps of Iranian oil, President Barack Obama has to sell the deal to a hostile Republican Congress that has 60 days to review it.

Obama has vowed to veto any legislation that may scuttle what he described as "a comprehensive, long-term deal that will verifiably prevent Iran from obtaining a nuclear weapon".

Asserting that "it would be irresponsible to walk away from this deal", Obama said he would "welcome a robust debate in Congress on the details of this deal" even as he warned that "I will veto any legislation that prevents the successful implementation of this deal."

"Because of this deal, Iran will not be able to produce highly enriched uranium or weapons-grade plutonium, the raw materials necessary to build a bomb," Obama said in an open letter to the American public explaining "what this deal means and how it works".

Under this deal, Iran will reduce its stockpile of enriched uranium by 98 percent, remove two-thirds of its installed centrifuges — the machines necessary to produce highly enriched uranium – and store them under constant international supervision, he said.

"Under this deal, Iran will modify its nuclear reactor in Arak so it cannot produce weapons-grade plutonium — and all spent fuel from the reactor will be shipped out of the country indefinitely," Obama said.

Asserting that "This deal is not built on trust – it's built on verification", he said international nuclear inspectors will have access to Iran's nuclear program – "where necessary, when necessary".

"As Iran implements this deal, it will receive gradual relief from sanctions. If it violates any aspect of this deal, sanctions that have crippled Iran's economy will snap back into place," he said.

According to the White House, the sanctions would begin lifting once the UN Security Council endorses the Joint Comprehensive Plan of Action (JCPOA) as the agreement is called, "simultaneously with the IAEA-verified implementation of agreed nuclear-related measures by Iran".

So it's still some more time before Iranian oil starts flowing freely again to India, which has reduced its oil imports from Tehran to 10-11 million tonnes in 2014-15 from 21.20 million tonnes in 2009-10. (IANS)