Exxon Mobil plans to sell up to $25 billion in oil and gas fields in its biggest asset sales for decades in Europe, Asia and Africa, aiming to free up cash to spend on a few mega-projects, sources said.

The sell-off would be a substantial reversal of the prior divestment efforts of the US energy company. It would be an aggressive effort by Chief Executive Darren Woods to catch up to rivals who undertook extensive investment assessments and selling swaths of capital after the market crash of 2014.

Throughout recent years, Exxon's stocks have underperformed their major rivals. The stock sale would help the company on new developments and appease unhappy investors with weak cash generation and oil output, flatlining under Woods' predecessor Rex Tillerson.

According to the three bank sources with direct knowledge of the project, revenues would see Exxon essentially leave its offshore oil and gas company in Europe. To invest in new developments in Guyana, Mozambique, Papua New Guinea, Brazil, and the United States, they would need to loosen up its financial reserve.

An Exxon spokesman declined to comment on individual properties that had been offered for sale but acknowledged that he had assured Wall Street investors that his asset sales could hit $25 billion by 2025.

According to a Reuters report, stocks in the world's top-listed energy company increased by 1.5 million. The Texas-based firm has assembled a comprehensive list of properties it needs to sell in recent months, covering at least 11 states, sources bared.

The number, whose specifics have not been published previously, will easily exceed its existing divestment goal, which envisages selling about $15 billion in capital by 2021.

Over recent months, Exxon has made a number of acquisitions, including a $4.5 billion Norway sale, and is already selling properties over China, Nigeria, and Malaysia.

According to reports, the revised project will also see Exxon spinning off assets in the British North Sea, France, and Romania. Throughout Europe, that would leave it only in the Netherlands for output, where it owns a share in the massive Groningen gas field with Royal Dutch Shell.

The new plan would also see Exxon dramatically change activities in Southeast Asia with the disposal of its properties in Indonesia and Malaysia, sources added.

Exxon is set to increase its spending sharply in the coming years to develop new oil and gas projects. Due to an uncertain outlook for oil prices and increasing pressure from investors to diversify from fossil fuels to renewables, most of its peers have become more cautious on their investments.