OPEC and its allies participating in a pact on curbing oil supply will take "strong" decisions at a meeting in December to ensure a stable market in 2020, OPEC's secretary general said on Thursday.

"The conference will take appropriate, strong, positive decisions that will set us on the path of heightened and sustained stability for 2020," Mohammad Barkindo told reporters at a briefing in London.

"All options are open," he said, when asked about the prospect of a deeper oil supply cut in December.

(Reporting by Alex Lawler; Editing by Edmund Blair) ((alex.lawler@thomsonreuters.com; +44 207 542 4087; Reuters Messaging: alex.lawler.reuters.com@reuters.net))