Washington's withdrawal from the landmark Iran nuclear deal was criticized across the world.
On Wednesday, U.S. officials told reporters the naval fleet of Iran's Islamic Revolutionary Guard Corps (IRGC) is planning to use 100 gunboats in the Persian Gulf to practice "swarm" tactics, an exercise that is usually reserved for the fall.
She added that while China may not cut Iranian oil imports, it did not indicate that it will increase imports either, raising the question of whether or not there will be 1 million barrels per day of Iranian oil take off the market by the end of this year and whether OPEC can make up for the shortfall.
To keep its shipment flowing Iran has offered insurance for oil cargo and ships to supply oil to India, its top oil client after China.
Preliminary tanker arrival data cited by Reuters on Thursday showed that the Asian country increased purchases of Iranian crude by about 30 percent to a record 768,000 barrels per day (bpd) as state refiners' intake surged ahead of U.S. sanctions in November.
Trump unilaterally withdrew the United States from the multilateral deal with Iran in May and announced plans to reimpose sanctions on the Islamic Republic, that would eliminate Tehran's oil revenues.
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India's oil imports from Iran last month soared by 85 percent from the 415,000 bpd shipments in July 2017, according to the data obtained by Reuters.
But all Iranians are concerned about the struggling economy, especially since the United States walked out of the nuclear deal in May and announced it would reimpose full sanctions in two stages.
The US is due to impose a series of new sanctions on Iran in the next few months.
Iranian President Hassan Rouhani has warned the USA against any attempt to stop Tehran's oil trade, threatening to block the strategically important Strait of Hormuz.
European countries, along with Russian Federation and China, remain committed to the nuclear deal, but European companies are unlikely to risk USA sanctions to do business with Iran. USA officials last week said Iran carried out a similar exercise, though Tehran did not immediately acknowledge it.
The official confirmed that during July delegations would be dispatched to Beijing and Delhi to press home the case, having already visited the capitals of other major Iranian oil importers.
USA crude exports have been seesawing over the past month, falling 51 per cent last week after an 84 per cent increase the week earlier, according to the latest Energy Information Administration Data.