Strasbourg, France/Baden-Baden, Germany  - Turkey vetoed Friday the appointment of Danish Prime Minister Anders Fogh Rasmussen as the next NATO secretary general, souring the start of the alliance's 60th anniversary summit in France and Germany.

"We either have consensus or we don't ... and we have no consensus yet," said NATO spokesman James Appathurai when asked whether heads of state and government had reached a deal on the successor to the current chief, Jaap de Hoop Scheffer.

Appathurai said the talks would resume on Saturday, but denied claims that they would steal valuable time from planned discussions on NATO's operations in Afghanistan.

"Have no doubt that (NATO leaders) will devote all the time necessary to the Afghanistan discussion. This is our number one operational priority," Appathurai said.

"If they need more time to discuss other issues, including the succession issue, they will take it," he said.

The failure to reach an agreement was a slap in the face of German Chancellor Angela Merkel, who earlier Friday predicted a deal by the evening.

Rasmussen, who officially announced his candidacy to his cabinet before heading for the summit, was still in contention but he continued to face considerable resistance from Muslim Turkey, which resents his decision not to intervene in the 2005 and 2006 Prophet Mohammed cartoons crisis.

Turkish Prime Minister Recep Tayyip Erdogan, who was not present at the talks, had also complained Friday about Denmark's hosting of Roj TV, a satellite broadcaster with close ties to the separatist Kurdish Workers' Party (PKK).

During Friday's dinner-time talks, NATO leaders also discussed how to improve the alliance's relations with Russia, strained by its August invasion of Georgia, an aspirant NATO member.

Appathurai said a meeting of NATO foreign ministers with their Russian counterpart would now likely take place in May.

Most of the day saw US President Barack Obama steal the show, receiving a rock star's welcome and thrilling Europeans with calls for a nuclear-free world during meetings with French President Nicolas Sarkozy in Strasbourg and with Merkel in Baden-Baden, across the Rhine River.

While in Strasbourg, Obama also found time to hold a question-and- answer session with young students, in which he announced he would urge European Union governments to pursue a nuclear-free agenda at Sunday's EU-US summit in Prague.

"Even with the Cold War now over, the spread of nuclear weapons or the theft of nuclear material could lead to the extermination of any city on the planet," Obama said.

"And this weekend in Prague, I will lay out an agenda to seek the goal of a world without nuclear weapons," he added, to loud applause.

Earlier in the day, Obama was enthusiastically cheered by spectators when he and his wife, Michelle, arrived at Strasbourg's Palais de Rohan for talks with Sarkozy.

Smiling and visibly touched, Obama greeted the spectators with handshakes and calls of "Nice to see you" and "It's good to be here." At one point, he even leaned into the crowd to kiss a young woman.

Attending his first NATO summit, Obama sought to cajole Europeans by promising to listen to their concerns.

"I've come to Europe this week to renew our partnership, one in which America listens and learns from our friends and allies, but where our friends and allies bear their share of the burden. Together, we must forge common solutions to our common problems," Obama said.

But he also presented them with a stark reminder that they should do more if NATO is to defeat the Taliban insurgency and prevent Afghanistan from becoming a safe-haven for al-Qaeda terrorists.

"We will all now have to make additional and sustainable efforts to succeed" in Afghanistan, he said, after talks with Merkel.

The United States' European allies have long been under pressure to contribute more soldiers, trainers and money to NATO's International Security Assistance Force (ISAF) in Afghanistan, whose 62,000-strong force includes about 30,000 American soldiers.

France, Germany, Italy and Britain are among the European nations that have announced plans to provide more trainers or boost their military in Afghanistan, particularly during the country's presidential elections in August.

Sarkozy praised the new "spirit of openness" in Washington since Obama replaced George W Bush as the country's president.

"It is damn good news to have a US president who knows that the world does not end at the borders of his country," said the French president.

Sarkozy also promised to host some of the detainees being released from the United States' notorious Guantanamo Bay prison camp in Cuba, which Obama has vowed to close by the end of the year. (dpa)