The Organization of the Petroleum Exporting Countries and partners including Russia, an alliance known as OPEC+, have been considering since last month moving the date of their policy meeting in Vienna to July 3-4 from June 25-26.

Russia's Alexander Novak favours postponing the meeting to early July to avoid clashing with G20 discussions in Japan in late June, while the Iranian minister, Bijan Zanganeh, wants to keep the original schedule, sources have said.

The two are scheduled to meet at 5 p.m. Tehran time (1230 GMT), one of the sources said.

"Hopefully this meeting will break the impasse," the source said.

OPEC and its allies have been reducing oil output by 1.2 million barrels per day since Jan. 1 to support the market. The meeting is to decide whether to extend or adjust the pact.