Asian imports of Iranian crude rose to the highest level this year in May, although buyers may have to curb any further increases if negotiators up against a deadline fail to reach a final deal on Tehran’s disputed nuclear programme.

A deal between Iran and six world powers would resolve a 12-year standoff over the Islamic nation’s nuclear work in exchange for relief from sanctions, which could eventually send millions of barrels flooding into an already saturated market.

Iran has as much as 40 million barrels of oil stored in tankers and aims to increase output by 500,000 barrels per day (bpd) within a month of sanctions being lifted and up to 1 mbpd within six or seven months.  Iran, the US, Britain, France, Germany, Russia and China reached a tentative framework for a nuclear pact on April 2 but several issues remain unresolved. They had a self-imposed June 30 deadline to arrive at a comprehensive agreement and talks are now expected to stretch into July.

“I think we will probably have to wait six months till we see officially sanctioned exports out of Iran going forward,” said David Fyfe, head of market research and analysis at Gunvor in Singapore.

Imports by Iran’s four biggest buyers – China, India, Japan and South Korea – totalled 1.2 mbpd last month, down 1.9 per cent from a year ago and the highest since 1.21 mbpd in December, government and tanker-tracking data showed.