By Rania El Gamal

SINGAPORE, Sept 9 (Reuters) - Iran has told OPEC it pumped 3.63 million barrels of oil per day (bpd) in August, up 10,000 bpd from July, an OPEC source said, marking a slowdown in the rapid growth that followed the lifting of Western sanctions in January.

Iran has been the main factor preventing an output deal between OPEC and non-OPEC Russia to boost prices, as Tehran has said it should be excluded before its production recovers. Renewed talks on an output pact are under way.

The Iranian production figure is due to be published on Monday in the Organization of Petroleum Exporting Countries' next monthly report. The report will also show the secondary sources OPEC uses to estimate its output also see Iran's August production at 3.63 million bpd, unchanged from July.

The latest OPEC figures suggest Iranian production has reached the level it pumped in late 2011, before the last round of sanctions were tightened leading to a drop in Iranian exports.

(Reporting by Rania El Gamal, Writing by Alex Lawler; Editing by Mark Potter) ((; +971 562 160 434; Reuters Messaging: