The four new vessels will replace higher-cost capacity in the very competitive trans-Pacific trade.

Designated as ''Express Class,'' the 4,000 TEU (20-foot equivalent units) vessels are being built to comply with the highest international standards and will operate at a speed of 24 knots.

Sea-Land will be signing contracts with Ishikawajima-Harima Heavy Industries calling for construction at the company's Japanese shipyards.

The vessels will be delivered in the second half of 1995 and early 1996.

CSX chairman and chief executive officer John Snow said: ''This commitment attests to our confidence in Sea-Land and its long-term prospects in the burgeoning global trade arena.'' Sea-Land has registered impressive income gains in recent years by taking decisive steps to increase productivity, reduce costs and increase its competitive advantage, he said.

''The timing is right. Shipyard prices are attractive and we expect to realise highly satisfying returns on these important vessel assets, Mr Snow said.'' Sea-Land president and chief executive officer John Clancey said: ''This programme enables us to replace higher-cost assets, improve efficiency and enhance service to our customers.'' The new high-speed vessels are designed for world-class, express service between the US West Coast and Asia.

They will be supported by an unsurpassed infrastructure of terminals, intermodal connections and information and logistics networks in both continents, offering shippers a high value-added distribution system.

Sea-Land also is close to concluding agreements to modify three US-flag, 3,800-TEU Atlantic Class vessels (ACVs), originally built by the former United States Lines in 1985 and purchased by Sea-Land in 1988, into Global Class vessels.

Modification would increase their service speed to 21 knots from the current service speed of up to 19 knots.

That will enable the company to deploy these vessels as replacement tonnage in any of several key trade lanes.

The modified vessels will retain a container capacity above the average TEU level currently obtained in the Atlantic Class vessels.

Sea-Land is evaluating bids by finalists for this shipyard work, which will be completed late this year.

Mr Snow said: ''The company plans to operate the vessels to be modified under the US flag, assuming maritime reform is enacted in this session of Congress.

''We would welcome the opportunity to operate the new vessels under US flag as well, if the reform package is appropriately funded and if it adopts international standards for vessel specifications.'' With revenues of US$3.2 billion last year, Sea-Land is a world leader in intermodal freight transportation and related services.

The company operates more than 80 container ships and 158,000 containers in US and foreign trade, serving 100 ports in 70 countries and territories around the world.