Finland's Containerships has not yet taken a decision on whether to declare its final two LNG-fuelled boxship options in China.
The company firmed up ships five and six in the series at Guangzhou Wenchong Shipyard in the summer.
But CEO Kari-Pekka Laaksonen told TradeWinds there are currently no talks taking place over the last two contracts.
He added that construction of the latest two vessels will start towards the end of next year and they should be delivered in early 2021.
The 1,400-teu units, partially powered by LNG, are being built in co-operation with shipmanagement company Nordic Hamburg.
Containerships is the main owner of the first four units.
The initial order was placed in 2014 at Yangzhou Guoyu for $32m each. The yard was later switched to ensure delivery dates were adhered to.
But the vessels have been delayed nevertheless due to the new technology involved.
