The EU's naval force for Somalia "Atalanta" mission, which consists of six warships and three maritime reconnaissance aircraft, is due to start escorting merchant ships and World Food Program vessels delivering food aid to Africa on Monday.

The United Nations' Security Council gave its formal green-light to the EU mission, which is to last for one year at a cost of 8.3 million euros ($10.5 million) last week.

The EU force takes over from NATO's own flotilla, which has been patrolling the Somali coast since late October.

But as the EU force prepares to take over the responsiblility of patrolling the waters off Somalia, a number of factors are casting a shadow over the mission.

Earlier this week, EU foreign policy chief Javier Solana conceded that there were still a number of legal issues that needed to be resolved. One concerns the different rules which EU member states apply on the detention of pirates.

"We need to coordinate that, but every country has a position - and that position is that they will not allow pirates to play around," Solana said.

NATO commanders have also stressed the need for a more permanent solution to the patrols off the Somali coast. But officials note that any decision will likely require months of discussions.

"NATO is indeed studying a longer-term role ... but there's a lot of water on this globe, and this issue will be on the agenda for some time to come," the NATO chief said.

EU efforts were thrown further into doubt on Friday when Germany said that it would be reluctant to "actively" pursue Somali pirates under its commitments to the EU security mission unless national interests were at stake.

"Arresting people suspected of piracy is not the primary objective of the (German) operation," Foreign Minister Frank-Walter Steinmeier and Defense Minister Franz Josef Jung wrote in a letter addressed to lawmakers, according to ARD public television and Saturday's edition of Frankfurter Allgemeine Zeitung newspaper.

In the letter Berlin had drawn up a list of priority cases in which it is willing to deploy its navy to combat the pirates.

A decision setting out the terms of Germany's contribution to the mission is due to be made public on Wednesday.

"We must protect civilian boats in this order of priority: World Food Program boats, other ships delivering humanitarian aid, vessels from EU member states or involving a third country, (and) other boats," the document said.

The report has drawn criticism from Germany's opposition, which has accused the government of being too defensive.

"We must actively fight the pirates and take their boats. After all, a pirate without a boat is quite ridiculous," said Rainer Stinner from the liberal Free Democrats party (FDP).

Somali pirates undeterred by EU force

Meanwhile, Somali pirates were undeterred Saturday as the new EU naval forces readied to launch their operation aimed at curbing relentless attacks that have rattled world maritime trade in the Gulf of Aden, which has in recent months become the world's most dangerous stretch of water.

The Gulf of Aden commands access to the Red Sea and the Suez Canal, a key trade route between Asia and Europe, and Atalanta will attempt to reassure shipping companies.

Pirates equipped with speedboats, assault rifles and rocket launchers, have carried out more than 100 attacks since the start of the year.

They have raked in tens of millions of dollars in ransom money after hijacking foreign vessels, from luxury yachts to the Sirius Star, a 330-metre crude carrier which is still being held.

Arguing that foreign fishing fleets have for years plundered Somali fishing resources illegally, pirates have secured strong support from the coastal communities in a country ravaged by conflict and starvation.

"The presence of European war ships will undermine the Somalis' ability to protect their natural resources from illegal fishing," said Mohamed Said, a pirate leader whose group has held the Saudi super-tanker Sirius Star for ransom since November 15.

"Many of the polluters of Somalia's waters, those who dump toxic waste, are Europeans. This force will contribute to giving them unimpeded access to our waters," he told reporters.

Experts doubt multinational force is large enough

With five of six EU ships expected in Somali waters this month, the international naval presence in the region will be further enhanced, restricting the pirates' room for maneuver.

But despite the added support of NATO, the US navy and Asian powers, experts argue the number of war ships will remain insufficient to root out piracy.

According to UNOSAT, a UN-affiliated agency that analyses satellite data, the recent increase in naval vessels has done little to deter pirates, only forcing them to concentrate their attacks in specific areas.

Out of the 80 attacks reported in the past three months alone, half of them occurred in or around the so-called corridor which merchant vessels have been encouraged to use in order to benefit from navy monitoring.

While the success rate of the pirates' attacks has dipped slightly in recent weeks, the sheer numbers of attacks continues to thwart the West's state-of-the-art naval machine.

"You would need at least 100 naval ships in the area to make a decisive impact but this is impossible," said Jean Duval, a maritime expert with French private maritime security outfit Secopex.

Duval's firm, which expects to clinch contracts with shipping companies in the coming weeks, is one of dozens of private companies hoping to cash in on the surge in piracy in Somalia's strategic waters.

While navies only can actively combat piracy and detain pirates, private firms seek to offer complementary services by escorting ships through the Gulf of Aden.

The EU and its international partners are aware of the limits to their action, admitting that piracy can only be eradicated if durable solutions are found to stabilize Somalia.

"Everything needs to be done to change Somalia from a failed to state to a country where the authorities are in a position to maintain law and order," Vice Admiral Gerard Vallin, who heads France's naval forces in the Indian Ocean, told reporters.

Navies have been powerless to free hijacked ships once they have been seized by pirates. Somali pirates are currently holding 16 ships and more than 350 crew.

Pirates gave the owner of the Sirius Star up to the end of November to pay a ransom of $25 million.