COPENHAGEN, (Reuters) – The United States will help to mobilise $100 billion a year by 2020 to help poor countries combat climate change, Secretary of State Hillary Clinton said on Thursday in a gesture aimed at breaking deadlock in UN talks.

But she added conditions including that the world works out a “strong accord” to combat global warming at U.N. talks in Copenhagen ending on Friday and that China offers transparency in the way that it curbs emissions.

“In the context of a strong accord, in which all major economies stand behind meaningful mitigation actions and provide full transparency as to their implementation, the United States is prepared to work with other countries toward a goal of jointly mobilising $100 billion a year by 2020 to address the climate change needs of developing countries,” she told a news conference.

“We expect this funding will come from a wide variety of sources, pubvlic and private, bilateral and multilateral, including alternative sources of finance,” she said. “This will include a significant focus on forestry and adaptation, particularly…for the most vulnerable among us,” she said. But she said China had to drop its opposition to allowing measurement, reporting and verification of its emissions curbs.

“It would be hard to imagine, speaking for the United States, that there could be the legal or financial commitment that I’ve just announced in the absence of transparency from the second biggest emitter, and now the I guess the first biggest,” she said. “There has to be a willingness to move toward transparency in whatever forum we finally determine is appropriate. So if there is not even a commitment to pursue transparency that’s kind of a dealbreak for us,” she said.