LONDON (Reuters) - Iranian oil exports are falling further in June as more customers in Europe and Asia stop or scale back purchases ahead of European Union sanctions aimed at slowing Tehran's nuclear program.
Crude exports from Iran so far this month have dropped to between 1.2 million barrels per day (bpd) and 1.3 million bpd, according to a firm that tracks oil shipments and sources at oil companies.
The latest decline, if confirmed, indicates Iran may have lost as much as 1 million bpd of oil exports - worth around $90 million a day - due to the threat of an EU ban starting July 1 which also bars EU insurance firms from covering Iran's exports.
"I understand Europeans don't want to touch it anymore and nothing is clear around exemptions for July," said a trading source at a company that used to buy Iranian oil.
Some European customers have been deterred because oil loading in Iran in June could not arrive at its destination until after the July 1 deadline.
"Whoever can take Iranian is backing out for July arrivals," the source said.
Iran's crude shipments in May were between 1.5 million bpd and 1.6 million bpd, according to the same sources, who declined to be identified by name because they are not authorized to speak to the media.
As sales fall, Iran has been storing unsold oil on tankers in the Gulf. Earlier this week, Iran blocked off information showing how many tankers were storing oil at its main export hub, Kharg Island terminal.
Industry sources are keeping an eye on the potential for the stored oil to head into the market quickly, boosting exports, should buyers in Asia mop up the surplus, or the West and Iran make progress in talks on Iran's nuclear work.
Royal Dutch Shell, a big buyer last year, has now wound down its Iranian crude buying, an industry source said. Italy's ENI is still taking Iranian crude in June but does not currently plan to do so in July, another source said.
Some of Iran's major customers in Asia, though, are figuring out ways to keep imports flowing, although at overall reduced rates, despite the EU ban on insuring tankers.
Japan has secured a parliament approval that allows the government to provide insurance, while China is asking Iran to take on the risk and deliver the crude on their ships.
The EU in January embargoed purchases of Iranian crude but let those with existing contracts continue until July 1. The West suspects Iran is trying to develop atomic bombs, while Tehran says its nuclear work is solely for civilian purposes.
Last year, Iranian crude exports were running at about 2 million-2.2 million bpd with total production, including domestic consumption, at 3.5 million-3.6 million bpd.
There is no timely official data on Iranian crude export levels and there are often differences of opinion among those that monitor its supplies on the rate of shipments.
Iran in April conceded that its exports had fallen slightly to 2.1 million bpd from 2.2 million bpd at the end of last year.
Reporting by Alex Lawler; editing by James Jukwey and Keiron Henderson