BRUSSELS - The United States has told NATO allies it will back Danish Prime Minister Anders Fogh Rasmussen as the next head of the alliance, NATO diplomats and a U.S. source said on Saturday.

Rasmussen already has the support of European heavyweights Germany, Britain and France for the post of NATO secretary-general, but Washington had been considering backing Canadian Defense Minister Peter MacKay.

A U.S. source close to the administration of President Barack Obama said Washington had indicated its acceptance of Rasmussen after U.S. National Security Adviser General James Jones this month went to Denmark to visit him.

Two senior NATO diplomats confirmed Washington had signaled to allies its acceptance of Rasmussen.

There seems to be a general coalescence around Rasmussen, said one, adding that an announcement was expected at the April 3-4 NATO summit. The current secretary-general, Dutchman Jaap de Hoop Scheffer, steps down on July 31.

Another NATO diplomat said Rasmussen's appointment still needed the backing of all 26 NATO allies -- including mostly Muslim Turkey, which has voiced misgivings over Rasmussen linked to the row over a cartoon in a Danish newspaper in 2006 depicting the Prophet Mohammad with a bomb in his turban.

A senior NATO source predicted there would be no problems. Turkey doesn't want to be in a minority of one, the source said.

Rasmussen refused to apologize for the cartoons, which sparked riots and attacks on Danish embassies in several Muslim states, but which Western governments defended in the name of freedom of expression.

Rasmussen, 56, in office since 2001, has the reputation of a competent and focused leader who gets things done.

In 2003, when Denmark held the EU presidency, he hammered out a deal on membership for 10 new states, mostly from ex-communist central and eastern Europe.

He backed the 2003 invasion of Iraq, sent Danish troops there and has urged NATO members to send more troops to Afghanistan, where 750 Danish soldiers are fighting the Taliban.

Analysts believe Rasmussen would try to steer NATO to work more closely with the EU and the United Nations.

Other contenders for a post which traditionally goes to a European include Polish Foreign Minister Radoslaw Sikorski, Norwegian Foreign Minister Jonas Gahr Stoere and former British Defense Secretary Des Browne.

Speaking at a security conference in Brussels on Saturday, Sikorski said NATO should consider an eastern European for the post now that former Soviet bloc states had been in NATO for a decade.

He said this would help improve NATO's relations with Russia, though analysts say appointing an eastern European could in fact hamper NATO efforts to patch up ties with Russia damaged by Moscow's intervention in Georgia last year.

(Additional reporting by Paul Taylor; editing by Mark John and Tim Pearce)