Delays in the auction process for Subway have prompted US buyout firm Advent to stop working on a potential deal to acquire the sandwich chain, according to a report by Bloomberg, citing unnamed sources familiar with the matter.

According to Reuters's sources, Advent, which had been competing with other private equity firms including Roark Capital Group and London-based TDR Capital in the auction, is no longer actively pursuing a takeover.

Subway first announced in February that it was working with JPMorgan Chase & Co over a potential sale, which could see the business valued at between $9bn and $10bn, according to Bloomberg.

The auction, which initially drew about 20 bids, has been delayed after initial expectations that a winner would be chosen by July.