Mantle Ridge, which was founded by former Pershing Square Capital Management LP partner Paul Hilal, would be attempting one of the biggest leveraged buyouts since the financial crisis if it goes ahead with an offer. Aramark has market value of about $8.6 billion and a debt pile of more than $7 billion (6 billion pounds).

Mantle Ridge plans to push Aramark to explore a sale, and has also held preliminary talks with banks about raising debt financing for the bid, the sources said. There is no certainty the bid will materialize, the sources added.

Mantle Ridge and Aramark did not immediately respond to requests for comment.

Aramark shares rose on the news to end trading on Thursday up 6.6 percent at $34.89.

Based in Philadelphia, Aramark is a provider of food and uniforms to education, healthcare, business, sports and leisure establishments. Its main competitors include Cintas Corp and UniFirst Corp.

Aramark has been trying to grow its business in the face of increasing competition and tight labor markets. It has had private equity ownership twice before, the last time in 2006 in an $8.3 billion buyout by then-Chairman Joseph Neubauer with the help of a consortium that included Goldman Sachs Capital Partners, CCMP, JPMorgan Partners, Thomas H. Lee Partners and Warburg Pincus.

As a result, many of the cost savings that private equity investors would typically achieve in a buyout have been realized.

After leaving Pershing Square in 2016, Hilal placed a bet through Mantle Ridge on railroad operator CSX Corp by agitating to install former Canadian Pacific President Hunter Harrison as CEO.

While Harrison died unexpectedly less than a year into his four-year contract, his involvement put the company on track for a turnaround that boosted CSX's stock and generated strong returns for Mantle Ridge.

By seeking to put together an offer for Aramark as a way to spur it to explore a sale, Mantle Ridge would be emulating the tactics of other activist investors that use this approach, including hedge fund Elliott Management Corp.

(Reporting by Greg Roumeliotis in New York; Additional reporting by Harry Brumpton and Svea Herbst in New York; Editing by Bill Rigby)

By Greg Roumeliotis