The second meeting of the so-called contact group on piracy off the coast of Somalia will be attended by 24 countries. A first meeting was held in January. The two ministers of foreign affairs also said they want Nato to be given the authority to arrest and prosecute pirates.

On Saturday, a Dutch naval ship, 'De Zeven Provinciën', had to let seven Somalian pirates go after rescuing 20 Yemeni hostages and disarming the pirates. On Sunday, Nato troops thwarted an attack on a Norwegian tanker and had to release another seven pirates after a short detention.

Four-point plan

At a joint press conference with Verhagen, Clinton said letting the pirates go sent the "wrong signal".

"We are going to have to determine the best way to bring pirates to justice after they are captured and there will have to be additional discussion of this at Nato, as well. The minister and I agreed that we will take this matter to Nato," she said.

A similar European Union mission operating off the coast of Somalia has an agreement with Kenya, where several dozens of pirates who were apprehended by European navy soldiers are currently on trial. The Nato mission does not have such an agreement.

"If the Dutch navy had been operating under the EU, they could have turned over the pirates for trial," Clinton said. "Nato has not provided that authority so we need to coordinate this, we need to move very quickly to try to get this resolved."

The contact group meeting is part of a four-point plan to combat piracy, which also calls for freezing pirates' assets and strategies to secure the release of ships and crews held by pirates.

Clinton added that she was also sending an envoy to the Somali donors conference in Brussels on April 23 to improve the situation in lawless Somalia and help implement the plan.

Legal vacuum

Late Tuesday Somali pirates attacked a US freighter with rockets, apparently in revenge for an operation that freed a US captain last weekend. The freighter escaped the attack, but more vessels have fallen into the hands of Somali bandits. A French warship meanwhile intercepted a pirate "mother ship" and arrested 11 gunmen.

There is much confusion about where detained Somali pirates should be tried. In some cases countries have invoked "national interest" to prosecute pirates who attacked ships sailing under their flags.

In New York, the only survivor of the Somali pirate crew that hijacked the US ship Maersk Alabama last week was expected to be arraigned in a Manhattan federal courtroom on Tuesday. Abduhl Wali-i-Musi is the first person on trial for piracy in the US for more than a hundred years.

The Netherlands currently has six Somali pirates in custody who were arrested by the Danish navy during a foiled hijacking attempt of a ship sailing under the flag of the Dutch Antilles.

Dutch experts have called for a specialised piracy tribunal to fill the legal vacuum.