The World Trade Organization closed its biennial ministerial conference on Saturday with its chairman citing an improved atmosphere in the 153-member club but no concrete moves forward on the Doha round of world trade talks.

Little was expected from the meeting on Doha, a deadlocked negotiation that has caused a crisis of confidence in the global trade body.

Nigeria's Trade Minister Olusegun Olutoyin Aganga acknowledged in a chairman's statement, the least ambitious form of resolution, that the negotiations were stuck, with significantly different perspectives on the possible results that members can achieve in certain areas.

But speaking for himself, Aganga said constructive dialogue between ministers over the three-day meeting had improved the atmosphere and outlook for the WTO.

It is essential that we do not let this improved political mood dissipate. I believe the contacts among ministers here have created a promising basis for renewing the political dimension of the WTO in a lasting way, he said.

There were some successes in the meeting: Russia, Samoa, Vanuatu, and Montenegro were brought into the group, and a last-minute deal to seal a landmark reform of government procurement rules won agreement.

But the talks began on a sour note when China slapped punitive duties on large cars and sport utility vehicles imported from the United States in the latest move in a tit-for-tat trade spat.

U.S. Trade Representative Ron Kirk told Reuters he was troubled by China's tendency to retaliate, but said he did not believe the spat could be called a trade war.

WTO Director-General Pascal Lamy, whose second term as head of the WTO runs out in September 2013, said this would be his last appearance as director-general at a regular ministerial meeting of the WTO.

He declined to comment when asked if he might step down to stand in the French presidential election next year.

Asked if there were any candidates to succeed him, he said: The answer is no. And if there were, I would not tell you.

(Reporting by Tom Miles; Editing by Sonya Hepinstall)