Beleaguered sandwich chain Quiznos filed for bankruptcy protection in the U.S. on Friday to restructure its finances in the face of intense competition in the crowded fast-food arena.

Denver-based Quiznos said the move would not affect customers and said its almost 2,100 restaurants in 35 countries -- most of which are independently owned franchises -- would remain open.

The franchises are not part of the bankruptcy filing. Quiznos directly owns only seven stores.

The prepackaged restructuring is designed to cut the chain`s debt by $400 million US. In its Chapter 11 filing documents, Quiznos listed debts of more than $500 million US.

"Our business plan includes several key elements aimed at supporting our franchisees, including reducing food costs, implementing a franchise owner rebate program," Quiznos Chief Executive Stuart Mathis said in a statement.

The chain, founded in 1981, is facing an increasingly competitive fast-food market.  Its biggest rival, Subway, has 41,000 franchised restaurants in 100 countries.

The Quiznos bankruptcy filing followed a similar filing earlier this week by struggling pizza chain Sbarro.

With files from Reuters