VIENNA, May 25 (Reuters) - OPEC is debating on Thursday whether to include Nigeria in its pact to restrict oil production, two OPEC delegates said.

Nigeria and Libya, both suffering from unrest, were excluded from production caps agreed by OPEC and non-OPEC producers in December last year and effective from January until June 2017.

Saudi Energy Minister Khalid al-Falih said earlier on Thursday there was no plan to impose caps on Nigerian or Libyan production. Nigerian production has risen in recent months after several fields restarted production.

The Organization of the Petroleum Exporting Countries agreed on Thursday to extend production cuts by nine months, delegates told Reuters.

(Reporting by Alex Lawler and Ahmad Ghaddar; Editing by Dale Hudson) ((Dmitri.Zhdannikov@thomsonreuters.com;))