"We have noticed that the pirates are buying more and more sophisticated equipment, they're buying faster and more capable vessels, they are clearly using their ransom money for their benefit - both personally and on behalf of their piracy," she said. "We think we can begin to try and track and prevent that from happening."

Clinton said the administration will also call for immediate meetings of an international counterpiracy task force to expand naval coordination.

The US plans to send an envoy to an April 23 conference on piracy in Brussels. The US will also organize meetings with officials from Somalia's largely powerless transitional national government as well as regional leaders in its semiautonomous Puntland region to encourage them to do more to combat piracy.

Maritime experts say military force alone cannot solve the problem because the pirates operate in an area so vast as to render the flotilla of international warships largely ineffective. And with ships legally unable to carry arms in many ports, the world has struggled to end the scourge.

The Gulf of Aden, which links the Suez Canal and the Red Sea to the Indian Ocean, is the shortest route from Asia to Europe. More than 20,000 ships cross the vital sea lane every year. It is becoming more dangerous by the day.

In 2003, there were only 21 attacks in these waters. In less than four months this year, there have been 79 attacks, compared with 111 for all of 2008, according to the International Maritime Bureau.

Somali pirates are holding more than 280 foreign crewmen on 15 ships - at least 76 of those sailors captured in recent days.

On Wednesday, pirates released the Greek-owned cargo ship Titan and Greek authorities said all 24 crewmen were in good health. The ship was hijacked March 19.

The assault on the Liberty Sun delayed a reunion between freed American sea captain Richard Phillips and the 19 crewmen of the Maersk Alabama he helped save in an attempted hijacking last week. Phillips had planned to meet his crew in Mombasa and fly home with them Wednesday, but he was stuck on the Bainbridge when it was diverted to help the Liberty Sun.

Both the Liberty Sun and the Bainbridge could arrive in Mombasa on Thursday, according to a US official who spoke on condition of anonymity because he is not authorized to speak to the press about the matter.

The Alabama's crew left without him Wednesday, heading to Andrews Air Force Base, Md., on a chartered plane.

"We are very happy to be going home," crewman William Rios of New York City said. But "we are disappointed to not be reuniting with the captain in Mombasa. He is a very brave man."

A pirate whose gang attacked the Liberty Sun claimed his group was targeting American ships and sailors.

"We will seek out the Americans, and if we capture them, we will slaughter them," said a 25-year-old pirate based in the Somali port of Harardhere who gave only his first name, Ismail.

"We will target their ships because we know their flags. Last night, an American-flagged ship escaped us by a whisker. We have showered them with rocket-propelled grenades," said Ismail, who did not take part in the Liberty Sun attack.

(Agencies via China Daily March April 16, 2009)