June 24 (Reuters) - Temasek-backed Singapore conglomerate Keppel Corp (KPLM.SI) and Sembcorp Marine (SCMN.SI) are set to begin talks to explore combining their ailing offshore and marine (O&M) businesses, two sources familiar with the matter said on Thursday. A potential deal would bring together one of the world"s largestoffshore oil rig builders with smaller rival Sembcorp after the businesses were whiplashed by years of oversupply in the sector, sustained weakness in oil prices and a drop in new orders. "Consolidation is needed simply because of competition, and the need for bigger working capital to take on new and bigger projects," said Joel Ng at KGI Securities. Both companies own a network of shipyards in Singapore and overseas, including in Brazil, and employ thousands of workers. Trading in shares of Keppel and Sembcorp, which both count Singapore state investor Temasek Holdings(TEM.UL) as their largest shareholder, was halted on Thursday pending announcements. Sembcorp has a market value of S$2.4 billion ($1.8 billion), while Keppel, whose businesses include property and infrastructure, is valued at S$9.3 billion. Keppel declined comment while there was no immediate response from Sembcorp Marine to a Reuters query. Both companies are holding separate news conferences later on Thursday. The sources said boards of both companies are meeting to begin discussions that could take many months and ultimately result in Keppel Corp hiving off its O&M business and combining it with Sembcorp Marine, the sources said. The sources declined to be identified as they were not authorised to speak to media. Markets have been expecting a much-needed consolidation in the rig-building sector as companies in the shipbuilding and marine sectors in markets such as South Korea and China have already joined forces amid a weak sector outlook. Keppel"s shares have lost around 15% over the past 12 months, while Sembcorp has tumbled 40%. Last year, Temasek scrapped a $3 billion move to raise its stake in Keppel and take control, following Keppel"s poor performance. Then this year, Keppel said it was exploring options for its O&M business, as part of the group"s 10-year strategy to refocus its portfolio on energy and environment, urban development, connectivity and asset management. Market talk of a consolidation between the rig builders had first resurfaced in June 2020 when Sembcorp Industries (SCIL.SI), the former parent of Sembcorp Marine, unveiled plans to demerge its core business from the lossmaking rig builder. Then Temasek stepped in to support a $1.5 billion rights issue by Sembcorp Marine ($1=1.3458 Singapore dollars) Reporting by Rashmi Ashok in Bengaluru; Editing by Christian Schmollinger Our Standards: The Thomson Reuters Trust Principles.