Philly Shipyard has signed a letter of intent with a mystery US ship operator to build up to four containerships for the Jones Act trade.

The Aker-controlled shipyard said the deal contemplates two firm vessels and two options to serve the trade lane between Hawaii and the US mainland, where US-built ships are required by law.

The LOA takes advanced talks revealed in June to the next level, locking both sides into exclusive negotiations to hammer out a deal.