The challenges facing Nato in Afghanistan are set to dominate the agenda as leaders of the alliance meet in France for a day of summit talks, BBC reported.
On Friday, US President Barack Obama called for better use of Nato resources there, saying al-Qaeda posed a greater threat to Europe than to the US.
He wants European nations to commit more troops and funds, but so far new pledges have been limited.
Meanwhile, leaders have so far failed to agree on a new secretary general.
They had been widely expected to endorse a new Nato chief at a gala dinner held in Germany to open the summit on Friday.
Big European powers had backed Danish Prime Minister Anders Fogh Rasmussen to replace Jaap de Hoop Scheffer, who steps down at the end of July.
But Turkey expressed opposition, based on Mr Rasmussen's stance over the publication in 2005 by a Danish newspaper of caricatures of the Prophet Muhammad.
Many Muslims around the world were angered when Mr Rasmussen refused to censure the paper, invoking freedom of speech.
The disagreement is an embarrassing start, says BBC diplomatic correspondent Jonathan Marcus in Strasbourg, but leaders appear determined that this will not over-shadow a gathering intended to re-launch the alliance for the 21st Century.
The summit, jointly hosted by Germany and France, marks Nato's 60th anniversary.
Early on Saturday, Nato leaders will start by walking over a footbridge across the Rhine - a symbol of the unity and peace in Europe that Nato has helped to defend.
But the sternest challenges facing the alliance now lie thousands of miles away in Afghanistan.
The main business of Saturday's meeting in Strasbourg is to re-energise Nato to win a war that everyone accepts is not going very well, our correspondent says.
Last month, Mr Obama set out a new strategy for the conflict.
In addition to more troops, he wants to send more funding and trainers to build up Afghanistan's security forces, as well as expert advisors to reinforce the country's crumbling infrastructure.
Speaking in Strasbourg on Friday, he appealed to European leaders to unite in support of the fight against al-Qaeda in Afghanistan.
"It is probably more likely that al-Qaeda would be able to launch a serious terrorist attack in Europe than in the United States because of proximity," he said.
"This is not an American mission, this is a Nato mission, this is an international mission."
British Prime Minister Gordon Brown has offered a temporary increase in troops ahead of Afghanistan's presidential elections in August.
But despite European expressions of support for the new American strategy, it was not clear whether the long-term pledges sought by the US would be forthcoming.
Protesters have vowed to disrupt the meeting.
Security is very high in Strasbourg, with dozens of people arrested over the past two days.