COPENHAGEN: World leaders launched a last-ditch effort to save talks on fighting global warming on Friday as a select group of key leaders broke up to allow face-to-face talks between US President Barack Obama and Chinese Premier Wen Jiabao.

Diplomats at the talks said that China and the US had emerged as the main stumbling-blocks to a deal as they argued over how much right developed states should have to double-check developing nations’ reports on their greenhouse-gas emission reductions.

Friday had been scheduled as a day of negotiations between over 120 world leaders to fill in the final details of two legal texts on fighting global warming. The texts were meant to serve as the basis for future international treaties.

But the day quickly degenerated into a series of crisis meetings between the leaders of some two dozen heavyweight states such as the US, China, India, Brazil, and European and African nations.

Those talks were aimed at agreeing a much shorter and simpler political declaration, which would tell expert negotiators how to draw up the final legal texts in the next few months.

But they stalled as the row between the US and China appeared to grow increasingly entrenched.

Denmark, the beleaguered host of the talks, broke off the fourth mini-summit of top leaders to allow for a face-to-face meeting between Obama and Wen, diplomats said.

Obama and Wen failed to bridge their differences that turned more than 100 heads of state and government into hapless bystanders.

Officials in Copenhagen had said that an agreement between China and the US — which together account for more than 40 percent of world emissions — was essential to a deal aimed at keeping global warming in check.

The latest compromise draft under consideration by a select group of world power-brokers said rich countries should commit to a joint target of cutting greenhouse gas emissions by at least 80 percent by 2050 in a bid to keep global warming within 2 degrees centigrade.

Diplomats had hoped a deal between the world’s most powerful states would trigger approval of the compromise from the hundred other countries at the talks.

But the latest draft showed no sign of progress on the US-China row, which hinged on the question of how much right third countries should have to inspect each other’s greenhouse-gas emission claims.

Instead, it left a space in the text where leaders could insert a “consideration (on) US and China” — indicating that they were not even close to being able to suggest a compromise text.

Obama on Friday called for “transparency” on emissions reporting, but offered China an olive branch by stressing that the new openness should not come at the expense of national sovereignty.

But leaders said that China refused to budge on the issue, rejecting anything more than voluntary reporting to the rest of the world.

“One of the main problems is that China is still reluctant to accept the idea of external control,” French President Nicolas Sarkozy said at a break in talks.

The row threw Friday’s final session of talks among around 120 world leaders into disarray as the heads of around 20 crucial states withdrew into an inner sanctum to try and thrash out a political deal in a series of increasingly frustrated meetings.

The first victim of the row was the UN’s attempt to tease out the final details of two legal texts which would serve as the basis for future treaties on fighting climate change.