VILNIUS, April 21 (Reuters) - The United States urged NATO on Thursday to respond quickly to any request for help in the Darfur conflict, but France insisted the alliance could not be the "gendarme of the world".

Despite NATO hints it would be ready to help a 2,000-strong African Union mission struggling to monitor a shaky ceasefire in the region, the AU has so far not made any request for support.

But U.S. Secretary of State Condoleezza Rice, who raised the conflict at wide-ranging NATO talks in Lithuania, said it should be ready to offer help with logistics and planning if asked.

"If there is a request, I would hope NATO would activate quickly ... We all have a responsibility to do what we can to alleviate the suffering in Darfur," she said.

However French Foreign Minister Michel Barnier disagreed that there was a role for NATO in Darfur and stressed that Africans should retain the lead in peace efforts.

"NATO does not have a calling to be the gendarme of the world," he told a news conference at the same meeting.

The AU troops are not mandated as peacekeepers and have limited powers to protect civilians in Darfur, a region the size of France in western Sudan. Survivors of militia attacks have demanded that peacekeepers be sent into the war-torn region.

Tens of thousands have been killed and more than 2 million uprooted by two years of fighting between non-Arab rebels and the Arab-dominated government. Khartoum denies accusations it is backing militias known as Janjaweed.

FRENCH INFLUENCE

French officials see the European Union as better suited to helping in the region than NATO. The alliance's involvement would mean a further U.S. presence on a continent where former colonial power France is keen to retain strategic influence.

NATO Secretary-General Jaap de Hoop Scheffer, who has also mooted a role for the alliance in Darfur, stressed the aim was "not to have NATO boots on the ground" but to offer support.

"NATO has the most sophisticated planning machinery in the world," he told reporters.

The disagreement on Darfur came at NATO talks where France also rejected a U.S.-backed initiative to turn the alliance into a transatlantic forum for debate on broad strategic issues.

Washington backs proposals by de Hoop Scheffer to broaden the 26-member alliance's remit, seeing it as a way for its voice to be heard in European policy-making.

Rice on Wednesday described NATO as "the premier forum" for transatlantic political dialogue and said NATO allies should be able to use it to discuss any issue affecting them.

"We want to use NATO more, and more efficiently," she said.

But Barnier said key issues such as Iran's nuclear programme were better dealt with elsewhere and stressed that the EU insisted on full autonomy over its own policy decisions.