A U.N. panel on climate change plans to release a report that is critical of the Kyoto Protocol global warming regime, saying the international pact "has had limited effect on global emissions," a draft report said Thursday.

The third working group of the Intergovernmental Panel on Climate Change, which is meeting in Berlin, hopes to draw on the lessons of the Kyoto Protocol for mapping out by 2015 a post-Kyoto framework to tackle greenhouse gas emissions.

According to a copy of a draft of the report obtained by Kyodo News, the working group said the Kyoto pact had a limited impact because it could not stop developing countries from increasing emissions and because the United States, a major emitter, did not ratify it.

The 1997 Kyoto Protocol required developed countries to cut emissions by at least 5 percent from 1990 levels between 2008 and 2012. Developing countries, however, were not obliged to do so under the pact.

The working group — one of three working groups under the IPCC and in charge of assessing ways to reduce greenhouse gas emissions — is scheduled to issue its latest assessment report on Sunday.