The first OSCE summit in more than a decade ended in acrimony Thursday after failing to agree an action plan to sharpen the trans-Atlantic security group's reactions to future conflicts.

After marathon talks lasting until midnight, the summit managed to agree a declaration reaffirming the group's principles but attempts to agree a more ambitious text were stymied by bitter disputes over existing conflicts.

"Regrettably it has not been possible to agree yet on the comprehensive action plan," an EU diplomat said at a closing session marked by expressions of despair and mutual accusations.

Diplomats said that efforts to find a deal had been torpedoed by disagreements over Georgia -- with whom Russia fought a war in 2008 -- and the Armenia-Azerbaijan dispute over the Nargorny Karabakh region.

World leaders at the summit, hosted by Kazakhstan in its glitzy new capital Astana, had acknowledged that the Organization for Security and Cooperation in Europe (OSCE)'s ability to fulfil its aim of preventing conflicts in Europe and the former Soviet Union has waned in recent years.

Yet the 56-member group operates by consensus, meaning any single country can torpedo the final communique and a proposed action plan that diplomats hope will define the future role of the OSCE.

The failure to agree an "Astana Framework for Action" -- supposed to be a centrepiece of the summit -- was a blow for Kazakh President Nursultan Nazarbayev, whose country holds the OSCE chairmanship.

Nazarbayev had kept the talks going late into the night in a bid to snare some kind of respectable deal at the first OSCE summit since a 1999 meeting in Istanbul.

Putting a brave face on the failure, Nazarbayev said the declaration that was agreed was "historic" and would "give our citizens hope for a better world."

A particular stumbling block were attempts to put a reference in the statement to Georgia, which fought a war with Russia in 2008 over two breakaway regions which Moscow now recognises as independent.

The EU diplomat said the bloc would not renounce its insistence on Georgia's territorial integrity.

The summit was also marred by bellicose speeches from arch-foes Armenian President Serzh Sarkisian and Azerbaijan President Ilham Aliyev, each accusing the other of sabotaging talks to resolve the Nagorny-Karabakh dispute.

Most of the top leaders left after the first day of the summit, leaving their diplomats to agree a deal.

Nazarbayev scored a major coup by attracting dozens of world leaders to his hitherto little-known capital, whose shiny new buildings seem to arise out of nowhere in the vastness of the Kazakh steppe.

But the summit has also been criticised by some activists who say Kazakhstan's dubious rights record, especially on media and Internet freedoms, made it a poor choice.