July 30, 2012. Oil tankers able to haul at least 20 million barrels of Iranian crude signaled for China in July, highlighting one of the challenges the U.S. and Europe face as they pressure the Persian Gulf state over its nuclear program. At least 10 very large crude carriers controlled by Tehran- based NITC signaled for ports in the world's largest energy consuming nation. Each has the capacity to carry about 2 million barrels. Six tankers signaled they were sailing to China, adding to four that did so July 3, marking the largest monthly tally since Bloomberg began compiling snapshots of the company's fleet in April. The latest delivery will be Aug. 20. The European Union banned the purchase and insurance of Iranian oil from July 1. About 95 percent of the world's tankers were insured by companies following EU law before the embargo. The U.S. Treasury Department said it would freeze NITC's American assets. The West claims Iran's nuclear program is an attempt to make an atomic weapon while the country says it's for civilian purposes. China imported about 17 million barrels a month from Iran. At least 32 ships in NITC's 40-strong fleet of crude carriers provided signals within the past month. That compared with 33 in the corresponding period to July 3.