LONDON - OPEC+ is working on a complex deal to be agreed at its meeting on Sunday that will allow the group to extend some of its deep oil production cuts into 2025, three sources familiar with OPEC+ discussions said on Thursday.

OPEC+ has made a series of cuts since late 2022 amid rising output from the United States and other non-members, and worries over demand as major economies grapple with high interest rates.

The Organization of the Petroleum Exporting Countries led by Saudi Arabia and allies led by Russia, known as OPEC+, is currently cutting output by a total of 5.86 million barrels per day, equal to about 5.7% of global demand.

The cuts include 3.66 million bpd by OPEC+ members valid through to the end of 2024, and 2.2 million bpd of voluntary cuts by some members which expire at the end of June.

OPEC+ will begin a series of online meetings at 1100 GMT on Sunday.

The deal on Sunday could include extending some or all of the cuts of 3.66 million bpd into 2025 and some or all of the voluntary cuts of 2.2 million bpd into the third or fourth quarter of 2024, three sources familiar with the discussions said on Thursday.

The extension of some cuts into 2025 will likely be made conditional on OPEC+ agreeing new individual member output capacity figures later in 2024, two of the sources said.

OPEC+ is trying to agree new oil production capacity for its member countries by the end of 2024, an issue that has created tensions in the past because each nation's output target is calculated from its notional capacity.

"We expect OPEC+ could announce on Sunday a framework for 2025 and how to phase back some of the cuts," said Amrita Sen, co-founder of Energy Aspects think-tank.

The countries which have made voluntary cuts that are deeper than those agreed with the wider group are Algeria, Iraq, Kazakhstan, Kuwait, Oman, Russia, Saudi Arabia and the United Arab Emirates.

"We would not entirely rule out a plot twist - in the form of a deeper cut - given (Saudi energy minister) Prince Abdulaziz's (bin Salman) penchants for Hollywood twist endings," said Helima Croft from RBC Capital Markets.

Prince Abdulaziz has repeatedly said he likes keeping the oil market on its toes and promised to punish speculators.

The OPEC+ meeting may coincide with a secondary share offering in oil giant Aramco on Riyadh's Saudi Exchange - the culmination of a years-long effort to sell another chunk in one of the world's most valuable companies after its record-setting IPO in 2019 raised $29.4 billion.

(Reporting by Olesya Astakhova, Alex Lawler, Maha El Dahan and Ahmad Ghaddar, editing by Dmitry Zhdannikov, Simon Webb and Elaine Hardcastle)