The Subway sandwich chain announced Thursday that it reached a deal to be acquired by Roark Capital, a private equity firm active in the restaurant and prepared foods sectors.

Subway, which has nearly 37,000 restaurants in more than 100 countries, said the deal would combine the chain's "global presence and brand strength with Roark's deep expertise in restaurant and franchise business models," according to a press release.

Financial terms were not disclosed. The value of the deal was expected to be over $9 billion, a person familiar with the matter told AFP earlier this week.

The Wall Street Journal previously reported that a Roark offer of $9.6 billion had led a competitive auction.

That value would make the Subway deal the third biggest US acquisition in the restaurant business, with the biggest being Burger King's 2014 acquisition of Tim Hortons for $11.4 billion.

"Subway has a bright future with Roark, and we are committed to continuing to focus on a win-win-win approach for our franchisees, our guests and our employees," said Subway Chief Executive John Chidsey.

Atlanta-based Roark already owns many brands including Buffalo Wild Wings, Baskin-Robbins and Seattle's Best Coffee, as well as other assets including Orange Theory gyms.

Roark did not immediately respond to a request for comment from AFP.

Neil Saunders of GlobalData Retail said Roark's strong operating experience will help Subway "especially in the US market where it remains well below the peak it hit a few years ago."

Subway was launched with a single sandwich shop in Connecticut by Fred DeLuca, who started with an initial $1,000 investment from family friend Peter Buck, as a way to pay his college tuition.

The two men famously started the venture based only on a handshake. DeLuca died in 2015, while Buck passed away in 2021.

In recent times, Subway executives have highlighted cost-cutting efforts to better compete with other restaurant chains, while focusing most growth efforts overseas.

In June, Subway unveiled a franchising agreement to open some 4,000 restaurants in mainland China over the next 20 years.