HOUSTON, Aug 10 (Reuters) - Exxon Mobil Corp has begun marketing U.S. shale gas properties as it ramps up a long-stalled program that aims to raise billions of dollars to shed unwanted assets and reduce debt taken on last year. The top U.S. oil producer three years ago set a goal of raising $15 billion from sales by December. More recently, it promised to accelerate lagging sales to whittle a record $70 billion debt pile. The company’s XTO Energy shale unit is seeking buyers for almost 5,000 natural gas wells in the Fayetteville Shale in Arkansas, spokeswoman Julie King confirmed. Exxon is marketing the properties itself and aims to receive bids this month, people familiar with the matter said. “We are providing information to third parties that may have an interest in the assets,” King said. No buyers have been identified, she said, declining to confirm the August call for bids or the company’s anticipated value on the wells. Exxon has achieved about a third of its three-year, $15 billion target with activity and asset values down during the pandemic. It has received sales proceeds of $557 million through June and has deals pending valued at more than $2.15 billion. Exxon acquired the Fayetteville assets here in 2010 for $650 million amid a shale boom that would change the U.S. energy landscape. The boom led to an oversupply of gas that pushed prices to record lows and last year led Exxon to reduce the value of its U.S. oil and gas holdings by $17.1 billion. The Arkansas properties cover some 416,000 net acres (1,680 square kilometers) and are some of the North American natural gas resources cut last year from Exxon’s development plan. The sale includes 844 operated and 4,104 non-operated wells, King said. Exxon, suffered a historic $22.4 billion loss in 2020, and its divestment program covers dozens of properties in Asia, Africa, the United States and Europe. The company is prioritizing debt reduction and its shareholder dividend, officials said last month. After total debt last year doubled to almost $70 billion since 2018, Exxon paid off more than $7 billion this year, to reduce its burden to $60.6 billion. This year, it has held talks with Britain"s Savannah Energy over properties in Chad and Cameroon here and sold stakes in two deep water oilfields to Occidental Petroleum and other. Exxon is seeing new interest in its properties with this year’s rebound in oil and gas prices, said Exxon Senior Vice President Jack Williams on July 30. “That whole divestment discussion that we’ve had in the past continues,” Williams said. (Additional reporting by Shariq Khan in Bengaluru; editing by Gary McWilliams and Marguerita Choy) Our Standards: The Thomson Reuters Trust Principles.