Subway
Subway was founded by then 17-year-old Fred DeLuca and his family friend Peter Buck. Image Credit: Supplied

Sandwich chain Subway has agreed to sell itself to private equity firm Roark Capital, the company said on Thursday, amid its struggles with intensifying competition and rising costs.

The terms of the deal were not disclosed, but Reuters reported earlier this week that Roark was in the lead to acquire the privately held restaurant company for well over $9 billion.

Roark, which has $37 billion in assets under management, controls Inspire Brands, the owner of restaurant chains including Jimmy John's, Arby's, Baskin-Robbins and Buffalo Wild Wings.

Subway has been owned by its founding families since its first outlet opened in 1965 as "Pete's Super Submarines" at Bridgeport, Connecticut. It was founded by then 17-year-old Fred DeLuca and his family friend Peter Buck.