Iran has beefed up its oil tanker fleet with vessels from China and is selling more crude to Beijing as Tehran struggles under international sanctions, the IEA said in a report Friday.

Iran's once lucrative oil sector has been crippled by sanctions imposed by the United States and the European Union over Tehran's controversial nuclear drive. Despite Iranian denials, the West is convinced Tehran is pursuing a nuclear bomb.

In its monthly oil market report, the International Energy Agency said Iranian crude oil production in July fell back to 2.6 million barrels per day (mbd) -- 50,000 million barrels less per day from June.

In contrast, however, the IEA said that preliminary data show that Iranian crude oil exports climbed to 1.16 mbd from just 960,000 barrels per day in June, mainly owing to a rebound in Chinese imports which last month rose to 660,000 barrels of oil per day from 385,000 the month before.

"Just five countries reported importing crude from Iran in July -- China, Japan, South Korea, Turkey and the United Arab Emirates," the IEA said, noting the number of countries totalled as many as 16 in January 2012.

Despite this, the IEA said "Iran continues to expand its shipping fleet in a bid to sustain crude sales in the wake of increasingly stringent international sanctions".

Since May, it has added four more supertankers, known as VLCCs, to its fleet, which now totals 37 VLCCs and 14 smaller crude tankers.

Most of the additions come from China as part of a 2009 deal to buy 12 VLCCs for $1.2 billion (898 million euros).

"The expanding shipping fleet should provide the state oil company more flexibility in marketing its crude and for use in floating storage," the IEA said.

In his first news conference since taking office, Iran's new President Hassan Rowhani earlier this month said he is determined to find a solution to the nuclear programme issue. The IEA said that although analysts are still sceptical, "markets warmed to the tone".