Turkey has offered four frigates, a submarine and a support ship to help NATO enforce a UN arms embargo on Libya, the military alliance has said.

Brigadier Pierre St Amand, a NATO military officer, said the alliance had so far received offers of 16 ships from a number of countries to implement the mission.

He said the ships included: a command-and-control ship from Italy; 10 frigates, including four from Turkey and one each from Britain, Spain, Greece, Italy, Canada and the US; submarines from Spain, Italy and Turkey; and auxiliary ships from Italy and Turkey.

St Amand said the NATO mission was authorised to use armed force to enforce the embargo.

Turkey, a NATO member, has said the air campaign over Libya led by France, the US and Britain has already gone beyond the scope of last week's UN Security Council resolution to enforce a no-fly zone and protect civilians.

In a speech to his ruling AK Party on Tuesday, Recep Tayyip Erdogan, the country's prime minister, said Turkey "will never point a gun at the Libyan people" and would explain its position to NATO allies.

The BBC reported on Wednesday that Abdullah Gul, the Turkish president, had cautioned the international coalition not to follow any hidden agenda over its operations in Libya.

Gul said it was "obvious" that some coalition countries saw the conflict as an opportunity for themselves.

The NATO mission will have the means to intercept and board suspicious ships, and the authority to fire a warning shot across the bow, a NATO official said on condition of anonymity.

"If after inspection, doubts remain as to the legitimacy of the cargo, the vessel will be diverted to a designated port for further inspection," St Amand said.

The operation was officially launched late on Tuesday after envoys of the 28-nation alliance gave the green light.

UK summit

William Hague, the UK foreign minister, said on Wednesday that Britain would host an international conference in London next Tuesday to discuss progress on the Libyan intervention.

"At the conference we will discuss the situation in Libya with our allies and partners and take stock of the
implementation of UN Security Council Resolutions 1970 and 1973," Hague said in a statement.

"We will consider the humanitarian needs of the Libyan people and identify ways to support the people of Libya in their aspirations for a better future."

Hague said a "wide and inclusive range of countries" would be invited, particularly from the region.

"It is critical that the international community continues to take united and coordinated action in response to the unfolding crisis," he said.

"The meeting will form a contact group of nations to take forward this work."

Earlier French officials said the meeting would be at foreign minister level and would include the African Union, the Arab League and the associated European countries.

'Technical role'

Meanwhile, Nato ambassadors held a third day of talks in Brussels to decide on the extent of NATO involvement in the UN-mandated mission.

The envoys are trying to reach agreement on who should lead military operations against Muammar Gaddafi's forces, with France saying NATO will have only a "technical role".

The US, Britain and France agreed on Tuesday that the alliance should play a key operational role, but the agreement of all 28 NATO states is needed and they have been split over whether it should also exercise political control.

There was no immediate word on whether Ankara would accept a compromise at the meeting.

France, which launched the air campaign against Libya with Britain and the US on Saturday, argues that having a US-led NATO in charge would erode Arab support because of the alliance's unpopularity in the Arab world.

Qatar has sent four warplanes, the United Arab Emirates has offered support, and David Cameron, the British prime minister, said Kuwait and Jordan had agreed to make logistical contributions to protect civilians in Libya. 

France wants to create an ad hoc steering group of member states of the coalition, including the Arab League, to exercise political control.

Laurence Lee, Al Jazeera's correspondent in Brussels, said the US, the French and the British had come to "some sort of accommodation with each other" but that there was still no final agreement.

Lee said: "On one level, the Americans, the British, have their way ... that NATO would run the military aspect of things and in turn the French would have their way, the Nato political command wouldn't be in charge and instead the plan says there would be a different sort of umbrella grouping.

"[This] would take in not just foreign ministers from Western NATO countries but foreign ministers from countries, for example, like Qatar or the Arab League ... to demonstrate a much bigger political umbrella and give a nod to the fact that NATO is acutely aware that this could be inflammatory to Muslim and Arab sensibilities."

One possible model would be the structure of the NATO-led International Peace Assistance Force in Afghanistan, in which non-NATO participating nations get a seat in the political steering group, diplomats said.

"For reasons of efficiency, we want a single command structure to run the coalition action, and NATO has such capabilities, so we must use its resources," Francois Baroin, a French government spokesman, said after a cabinet meeting in Paris.

"We are working to ensure that the coalition continues to retain the political leadership," Baroin said. "Talks with our allies are being finalised. It''s not quite nailed down yet."

Overnight movement

The US, Britain, Italy and Norway all want to put NATO in charge.

Turkey has said the alliance's role should be governed by several conditions, including an end to the military campaign as soon as possible.

NATO diplomats said there was a constructive mood going into Wednesday's meeting, but it was unclear if there would be an agreement.

A European diplomat said there appeared to be have been a shift in the French position following consultations between Cameron, Nicolas Sarkozy, the French president, and Barack Obama, the US president, overnight that could make a political deal possible.

"The line we now have is that NATO should have a key role in the command structure ... that's a little bit short of the lead role, but different from where France was a couple of days ago," the diplomat said.

Key to finding a deal would be to agree a mechanism which would allow for Arab involvement in the political leadership of the mission, the diplomat said.

Obama, under domestic pressure to limit US involvement, said on Tuesday he had "absolutely no doubt" a deal would be reached soon.

The question of who takes over leadership of the Libya mission is crucial for Obama, who has stressed limited US involvement to both voters and politicians worried about US forces becoming bogged down in another Muslim country while still occupied in Iraq and Afghanistan.