Washington, Dec 18 (DPA) US President Barack Obama departed for Copenhagen Thursday night for the last day of the UN-backed climate change summit with questions still remaining about whether an international pact can be reached.

Obama was to arrive in the Danish capital Friday morning to join 120 world leaders in the negotiations that began Dec 7. The goal is to come up with an international agreement to sharply reduce greenhouse gases, the main cause of global warming.

Optimism nudged slightly upward after the US and China, the two largest greenhouse gas emitters and critical to any agreement, appeared to grow closer in their positions.

Obama plans to meet with several leaders Friday, including Chinese Premier Wen Jiabao, according to the schedule released by the White House.

Agreement between China and the US, who together account for nearly half the world’s carbon emissions blamed for global warming, is seen as crucial by negotiators from around the world to reach a deal on fighting global warming.

Obama is also to meet separately with Danish Prime Minister Lars Lokke Rasmussen, Russian President Dmitry Medvedev and Brazilian President Luiz Inacio Lula da Silva.

Obama’s return time to Washington was left open, and would be determined later, the White House said.

The prospects for a deal appeared grim early Thursday when the Chinese initially appeared to balk at a demand made by US Secretary of State Hillary Clinton that Beijing be transparent in demonstrating compliance with any accord.

In a positive turn, Hu Yafei, a senior official from the Chinese foreign ministry, later told reporters in Copenhagen that “we promise to make our actions transparent”.

Analysts saw the move as a key step forward, but success will require intense diplomacy when talks resume Friday. The negotiations were also buoyed when Clinton, shortly after arriving in Copenhagen Thursday, said the US would back an international plan to provide $100 billion by 2020 to poor nations suffering from the effects of global warming.

Obama has been eager to show that the US is willing to clamp down on greenhouse gases after years of downplaying the issue.

Obama has embraced the issue and raised expectation even though his administration has been reluctant to go as far as the European Union wants. He has pledged to cut US emissions by 17 percent of 2005 levels by 2020.

EU officials have set a 2020 target of slashing emissions by 20 percent from 1990 levels, when emissions where even smaller.

Obama, coupled with his international popularity, is seen as a key broker in the discussions, and there are hopes that he will give the negotiations a badly needed boost.

At the same time, the White House expressed caution, saying no agreement is preferable to one that does little to tackle the problem.

“Coming back with an empty agreement would be far worse than coming back empty-handed,” White House spokesman Robert Gibbs said, according to CNN.