US President Donald Trump's administration dodged questions on whether it has firm commitments from India and China to stop all oil purchases from Iran within six months.
The administration said it is confident that "the toughest ever" sanctions against Iran which came into effect on Monday will have the intended effect to alter the Iranian regime's behaviour.
The sanctions cover Iran's banking and energy sectors and reinstate penalties for countries and companies in Europe, Asia and elsewhere that do not halt Iranian oil imports.
India and China -- the two biggest buyers of Iranian crude -- so far appear to have skipped the punitive American sanctions targeting the Iranian oil and financial sectors.
The two Asian giants are among eight countries that were given rare exemption from Iranian sanctions.
The Trump administration said it has asked these countries, which also includes Turkey, Iraq, Italy, Japan and South Korea, to bring down oil purchase to zero as soon as possible.
US Secretary of State Mike Pompeo, during a a talk show on Fox News, repeatedly parried questions when asked about the commitment from India and China on zero-oil purchase from Iran.
"Watch what we do. Watch as we've already taken more crude oil off the market than any time in previous history. Watch the efforts that President Trump's policies have achieved. We've done all of this, too, while making sure that American consumers don't suffer," he said, as he avoided giving a direct answer.
"I am very confident that the sanctions that will be re-imposed this Monday, not only the crude oil sanctions, that the financial sanctions that are being put in place by the Treasury Department and over 600 designations of individuals and companies in Iran will have the intended effect to alter the Iranian regime's behaviour. That's our expectation. It's the reason for President Trump's policy," he asserted.
India, which is the second biggest purchaser of Iranian oil after China, is willing to restrict its monthly purchase to 1.25 million tonnes or 15 million tonnes in a year (300,000 barrels per day), down from 22.6 million tonnes (452,000 barrels per day) bought in 2017-18 financial year, sources in New Delhi said.
The reimposition of US sanctions on Iran, Mr Pompeo asserted, are the toughest ever on this country.
"They're aimed at a singular purpose, denying the world's largest state sponsor of terrorists the capacity to do things like they did this past couple weeks, attempted assassination campaign in the heart of Europe," he said.
"These sanctions have already had an enormous impact. We've already reduced Iranian crude oil experts by over a million barrels per day. That number will fall farther. There's a handful of places were countries that have already made significant reductions in their crude oil exports need a little bit more time to get to zero, and we're going to provide that to them," he added.
The State Department did not respond to a question as to what will happen if India does not bring down its oil purchase from Iran to zero, as being demanded by it, in the next six months. It also did not respond to a question on the fate of the strategically crucial Iranian port of Chabahar, which India sees as critical for reaching landlocked Afghanistan and Central Asia.
In May, President Trump pulled US out of the 2015 Joint Comprehensive Plan of Action terming it as disastrous. Iran has dismissed these charges and continues to keep its stand that its nuclear programme is for peaceful purposes.
Brian Hook, the special adviser to the secretary of state and special representative for Iran, told PBS News that the US is not looking to give any exceptions or waivers to its sanctions regime.
"Going forward, next year, we anticipate a much better supplied oil market, and that will help us accelerate, I think, the path to zero," he said.