By Paul Adams BBC defence correspondent

The United States trumpets its broad coalition in the war on terrorism, but when it comes to military might, the alliance is still a narrow one.

And that, perhaps, is how Washington prefers it.

So far, only two countries have played a visible role in military action - the United States and Britain.

And Britain's contribution has been strictly limited. Submarines have twice fired cruise missiles at terrorist camps in Afghanistan, while refuelling and reconnaissance planes have offered critical support for American attack aircraft.

Italy has approved the deployment of 2,700 forces, including ground troops

It is generally assumed, but never acknowledged, that British special forces are also on the ground, performing a variety of secretive tasks.

But a host of other countries have now made offers of help:

The most recent was Italy, which approved a deployment of 2,700 troops including an aircraft carrier, helicopters, jets and parachute forces. Defence Minister Antonio Martino said some of them could see combat action.

Ottawa has promised ships, aircraft and as many as 2,000 soldiers. A single Canadian warship, HMCS Halifax, is on station in the Gulf.

France's President Jacques Chirac said on Tuesday that 2,000 "soldiers, sailors and aviators" were already involved in military operations.

Reconnaissance and transport planes and the electronic surveillance vessel, Bougainville, are already operating. Two other naval vessels are on patrol in the Indian Ocean.

In France, there have been complaints that Washington has been slow to take up its offer of help.

Germany's Chancellor Schroeder promised a large deployment

The German Government wants to send almost 4,000 troops, a concrete expression of what Chancellor Gerhard Schroeder describes as "unlimited solidarity".

But this momentous step - the biggest single German deployment since World War II - will not include ground troops, with the exception of 100 members of the country's special forces, the KSK.

The deployment will include Fuchs armoured vehicles (capable of detecting biological, chemical and nuclear contamination), airlift facilities and a naval presence. Parliament is expected to vote on the move next week.

Nato's only Muslim member, Turkey, last week took an equally symbolic step, committing 90 special operations soldiers to work on the ground inside Afghanistan.

Turkey - the only Nato member with a mainly Muslim population - will send 90 special forces

An official statement said their mission would include surveillance and assistance to the Northern Alliance. More than 100 members of parliament have asked the constitutional court to block the move.

Other countries, including the Czech Republic, Denmark, Italy, Spain, the Netherlands and Japan, have offered assistance or access to air space.

Special forces units from Australia and New Zealand were recently reported to be on the Indian Ocean island of Diego Garcia, ready to conduct operations in Afghanistan.

But while welcoming all expressions of support, Washington has yet to make much use of many of the offers.

Following the example of the Kosovo campaign, where every Nato member was involved in one way or another, the Bush administration is anxious to maintain a simple command and control structure.

"The more nations are involved, the more complex it gets," said a Nato official.

Military and political pressures pull in opposite directions

But military planning is sometimes easier than the political decision making that precedes it.

"The Americans are concerned about the core strategy being approved by everyone involved," said the Nato official.

A case, perhaps, of too many cooks spoiling the broth?

Inevitably, military necessity and political pressures tend to pull in opposite directions. Washington wants to avoid a situation where parliaments around the world have the ability to influence, and perhaps limit, the use of force in Afghanistan.

But the coalition against terrorism is a political alliance as well, and Washington knows that broad international support is vital.

Hence the Bush administration's talk of "several coalitions", in which members play a variety of political, military and financial roles.

Some members, officials admit, will not want to advertise the fact that they are involved. Washington is anxious to preserve a level of secrecy.

Access to what has been dubbed coalition village - at the Florida headquarters of the US Central Command, or CentCom - is highly restricted.

It was not until the end of October that military officials even confirmed the existence of the village, where a cluster of between 50 and 100 trailers house officers from Britain, Germany, Australia, New Zealand, Jordan, the Netherlands, Italy, France, Qatar, Turkey, Belgium and Canada.

As the military campaign drags on, it is likely that most, if not all of the countries that have offered assistance will have a chance to act.