BARCELONA, Spain -- The United States came under increased pressure yesterday to come up with a plan for fighting climate change and to offer an internationally acceptable policy for curbing the pollution that hastens global warming.

As U.N. climate talks reconvened, countries stepped up calls on Washington for specific commitments on reducing carbon-dioxide emissions and contributing to a global fund to help poor countries deal with the damage caused by climate change.

The five-day negotiating round in Barcelona is meant to prepare the text of a global-warming pact to be adopted at a U.N. conference next month in Copenhagen.

The deal would replace the 1997 Kyoto Protocol but require both industrial countries and developing countries to rein in emissions of carbon dioxide and other heat-raising greenhouse gases. Kyoto applied only to industrialized nations and was rejected by the United States.

Delegates to the Barcelona talks were showing frustration that after two years of negotiations, the U.S. has been unable to make firm commitments because it is waiting for Congress to enact legislation.

"We expect the United States to be able to deliver on one of the major challenges of our century," said Connie Hedegaard, the Danish minister of climate and energy, who will chair the meeting in Copenhagen.

U.S. chief delegate Jonathan Pershing said the U.S. intends to be part of a deal but would ensure that any deal it signed would be accepted by Congress. "We don't want to be outside an agreement," he said.