SANAA - Yemen said on Thursday it expected a North Korean ship carrying 15 Scud missiles and warheads to arrive at a Yemeni port within the next 48 hours and was not planning to buy more.

"We have signed a contract with North Korea to buy this shipment in 1999 and we have no intention to purchase any other shipment," a senior government official told Reuters.

Washington released the North Korean ship So San on Wednesday, two days after it was intercepted by Spanish warships in the Arabian Sea.

"We expect the ship to arrive any time within the next 48 hours. Perhaps today or tomorrow," the official said. He declined to give further details.

Spain has said 15 Scud missiles and conventional warheads as well as 85 drums of unidentified chemicals were found hidden under cement bags on the ship.

Yemeni Foreign Minister Abubakr al-Qirbi said on Thursday the missiles were bought for defense purposes.

"Yemen like every other country in the region is concerned about its security, about the stability of the region. Our objective is basically defensive," Qirbi told BBC radio. "Yemen made the deal based on cost effectiveness."

The release of the ship appeared to defuse a potentially explosive situation in a region where tensions have been high since the United States made clear it was prepared to go to war with Iraq over its suspected weapons of mass destruction.

White House spokesman Ari Fleischer said on Wednesday that Washington had freed the ship after it decided the missile shipment was not breaking the law and Yemen gave assurances it would not "transfer these missiles to anyone."

Asked if the U.S. action over the ship was understandable given that the weapons were hidden, Qirbi said: "I think it was an understandable act. The manifesto was not clear also. Once we discussed the matter with the Americans and they realized the correctness of the deal they released the ship.

"We appreciate that once the matter was clarified to the Americans the ship was released.

"I think the Spanish really have intervened incorrectly and I'm sure that once they realize the facts they will be apologetic about it."

Yemen, the ancestral home of al Qaeda leader Osama bin Laden, is trying to shed an image as a haven for Muslim militants.

It has arrested dozens of al Qaeda suspects in a major crackdown as part of the U.S.-led war against "terror."

The poor Arab state inherited an unspecified number of Scuds from formerly Marxist South Yemen after it united with the pro-Western North in 1990. Southern rebels used them against the north in the civil war of 1994.