The nations of the world expect the U.S. to "live up" to its pledge made last year in Copenhagen to cut greenhouse-gas emissions by 17% by 2020, the United Nations' official overseeing international climate negotiations said Wednesday.

The U.S. and other industrialized countries that have pledged to cut emissions of carbon dioxide and other gases linked to climate change will be expected to provide more details on how they plan to make the cuts at international climate negotiations scheduled to start later this month in Cancun, Mexico, said Christiana Figueres, executive secretary of the U.N. Framework Convention on Climate Change, which is hosting the negotiations.

European and other developed nations also have agreed to cut their greenhouse-gas emissions and in many cases have put those pledges into action with legislation or other domestic policies. The U.S. has not set policies to put its greenhouse-gas reduction pledge, made in December 2009 at climate negotiations in Copenhagen , into practice.

A proposal in the U.S. Congress that would implement the cuts has stalled and the outlook for the proposal has dimmed as the nation struggles against a weak economy and high unemployment. The U.S. Environmental Protection Agency is considering regulations that would require some greenhouse-gas reductions from energy and other industries.

The lack of legislative action in the U.S. , which along with China , is one of the world's largest emitters of greenhouse-gases, has made the outlook for an agreement at the upcoming climate negotiations in Cancun uncertain.

Figueres said that while a comprehensive global agreement on greenhouse-gas reductions may prove elusive in Cancun , she is confident that nations will reach agreement on some important climate-related issues such as protecting forests, sharing emission-reduction technology and creating a new fund to help developing countries pay for greenhouse-gas reduction activities.

In addition to those issues, Figueres said industrialized countries including the U.S. will be expected to provide details in Cancun about how they plan to make the emissions reductions they promised last year.

"All industrialized countries have quantified the effort they're going to make between [now] and 2020," Figueres said, speaking by telephone with reporters. "The challenge in Cancun is how to anchor those pledges into action."

With respect to the U.S. , if lawmakers don't take action to put the nation's pledge into action, President Barack Obama has pledged to take action through regulation, Figueres said.

"The United States has said repeatedly that they will honor that pledge through the regulatory track," Figueres said. "The world certainly expects the United States to live up to that pledge and comply with that."

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