Washington - At its first negotiations on climate change, the Obama administration is trying to persuade other countries that the United States does care about global warming and wants to shape an international accord.

    After eight years on the sidelines, the United States says it is ready for a central role in developing a new agreement to slash greenhouse gases. But whether the country, which is the second-largest source of heat-trapping pollution, is ready to sign onto a deal by year's end could depend on Congress.

    The State Department sent climate envoy Todd Stern to Bonn, Germany, for the first of a series of largely technical meetings that begin today. The talks are intended to lay the groundwork for an agreement to be signed in December in Denmark.

    Stern, in a telephone interview Thursday from London, said it was important for him to "make the first statement on behalf of the United States and say we're back, we're serious, we're here, we're committed, and we're going to try to get this thing done."

    Yvo de Boer, executive secretary of the United Nations Framework Convention on Climate Change, which is hosting the Bonn talks, said participants "will be very excited" to hear Stern outline the basic principles that will guide the United States.

    Other countries are expecting a new tone after the Bush administration made clear its disdain for any climate discussions aimed at securing a commitment to mandatory greenhouse gas reductions.

    This time the US delegation represents the views of a White House committed to mandatory action on climate change. And unlike 1997, when the Kyoto Protocol was drafted, there is now a Democratic-controlled Congress moving to embrace mandatory limits on greenhouse gases.

    Back then, the United States lacked support for mandatory actions to achieve the reductions it had signed on to. Congress never ratified that accord, and the Bush administration rejected it outright, citing the lack of participation from developing countries.

    But President Obama has acted to reduce US greenhouse gases and wants Congress to pass a cap-and-trade program that would cut global warming pollution 80 percent by mid-century.

    "The president has embarked on a strong domestic program already and there is much more coming," Stern said at a briefing Friday in Berlin.

    Stern said the US position on an international agreement will be framed by what happens in Congress. The reductions expected to be required by Congress will be the basis for what the country can commit to reducing, he said.

    But Congress already is trying to address the recession, healthcare, and other priorities. "This will be a big, big fight to get the domestic piece done," Stern said.

    Many European countries want the United States to adopt stronger short-term targets, equal to a 25 percent to 40 percent reduction from 1990 levels by 2020. Obama has called for reaching 1990 levels by then, a roughly 15 percent cut.