Norway's Ulstein Verft has signed a letter of intent (LOI) to build up to two expedition cruiseships in a breakthrough deal.

Designed by Ulstein Design & Solutions to incorporate the distinctive X-BOW design, the Ulstein CX104 will be 120 metres long and 20 metres wide.

Delivery is planned for 2019 and 2020 to an unnamed owner.

The yard said the vessels will become the most unique expedition units in the market, with polar capability "beyond anything we have seen before", while minimising environmental impact and optimising operational cost.

“The past few years we have worked strategically to target the exploration cruise market. This LOI proves that we are now confirming our position in this market," said CEO Gunvor Ulstein.

In March, Ulstein won a deal to design up to 10 cruiseships for Niels-Erik Lund-led SunStone Ships, to be constructed by China Merchant Industry Holdings.