By Trixie Yap, Siyi Liu and Chen Aizhu

SINGAPORE, April 25 (Reuters) - Aster Chemicals and Energy, the new operator of the Bukom refining complex, is planning to bid for Exxon Mobil's XOM.N petrol stations in Singapore, five people with knowledge of the matter said, as the refiner seeks retail fuel sales outlets.

The sale of the Exxon Mobil retail outlets is entering the formal bidding stage with binding offers due in May, two of the sources said. The network of 58 petrol kiosks is valued at roughly $1 billion, they said, although none of the initial bids have exceeded that level.

The sale has attracted the interest of private equity firms and asset managers, the same two sources said, although it was not clear which financial firms plan to bid.

The sale will mark Exxon's exit from Singapore's retail fuel sector as the government plans to reduce land transport emissions by switching to electric vehicles. In 2023, Exxon sold its gas stations in Thailand to Bangchak Petroleum BCP.BK for $603 million.

U.K. bank Barclays BARC.L is advising Exxon Mobil on the deal, the two sources said. All the people who spoke on the matter declined to be named as it is not public.

An Exxon spokesperson said the company does not comment on market speculation. Barclays and Aster Chemicals also declined to comment.

Aster, the joint venture between Indonesia's Chandra Group TPIA.JK and global commodities trader Glencore GLEN.L, recently acquired Shell's SHEL.L refining and petrochemical assets in Singapore in a deal that excluded the energy major's petrol stations.

"We continuously evaluate market opportunities where they align with our strategic priorities," Aster's spokesperson said in an emailed response.

(Reporting by Trixie Yap, Siyi Liu, Chen Aizhu and Yantoultra Ngui; Editing by Florence Tan and Tom Hogue)

((aizhu.chen@thomsonreuters.com; Reuters Messaging: aizhu.chen.reuters.com@reuters.net))