President Barack Obama strode into office backed by a Democratic majority in Congress and pledged to do something his predecessor had not: set mandatory limits on global warming gases and show that the U.S. was ready to tackle a problem it played a lead role in creating.

Nearly a year into his presidency, Obama and Democratic leaders in Congress have fallen short of their own expectations on climate change as they prepare to attend international negotiations that begin this week.

There's no chance this year of passing legislation to curb emissions of the gases blamed for global warming, although Democrats and the Obama administration had hoped to have it in hand by now to boost prospects for an international agreement.

After a strong start, global warming fell victim to a faltering economy, the decision to first take on health care, partisanship and Democratic infighting.

A further obstacle: an American public that says it supports action to reduce pollution from burning fossil fuels, but isn't willing to pay the higher energy prices that would probably come with it.

"We did not achieve the hopes that some of us had for this year ... a position that would give the president, as he goes to Copenhagen, a stronger voice," said former Sen. John Warner, a Virginia Republican who sponsored the last attempt in the Senate to pass a global warming bill.

Warner, in an interview with The Associated Press, said that part of the challenge for Obama and Congress was a public more concerned with pocketbook issues.

"It's going to take a long educational process to solidify the public base that is going to be needed to support a consequential piece of legislation," Warner said.

A poll conducted by the AP and Stanford University bears that out.

Eighty-five percent of the 1,005 people contacted said the government should do something about global warming. But most, when asked, don't want to pay too much for it.

By putting a price on carbon dioxide and other greenhouse gases, the cap-and-trade bill before Congress would raise costs for companies that release those pollutants when making electricity, gasoline or other commodities. It does this by putting a ceiling on emissions. The government gives companies a permit allowance equal to how much they pollute.

Those who pollute less than their allowance could sell the excess permits to other companies. Companies that cannot easily reduce emissions could buy permits to release more pollution.

The price provides an incentive for companies to reduce the output of greenhouse gases and transition away from fossil fuels. But the extra costs will ultimately be paid by consumers.

Government estimates say the average U.S. family would pay an additional $80 to $173 a year in energy costs under the bill narrowly passed by the House in June.

But the AP-Stanford University poll shows that the public is not willing to pay that much. More than half of the respondents said they wouldn't support a cap-and-trade program to reduce global warming gases if it increased their monthly energy bills by $10, or $120 annually. If monthly electric bills rose by $25 because of cap-and-trade, three-quarters of those surveyed said they would be opposed to it.

Republicans branded the climate legislation an energy tax and a jobs killer. That has caused centrist Democrats from states that rely on fossil fuels for energy or need them to supply energy-intensive industries to shy away from the issue.

With "a rather sick economy," the timing for overhauling energy policy couldn't have been worse, said Sen. Byron Dorgan, a North Dakota Democrat and one of the centrists opposed to the legislation.

"As a Cherokee Indian chief once said, `The success of a rain dance depends a lot on timing.' Well, that's especially true in American politics," Dorgan said.

Obama decided to make a personal appearance at the Copenhagen summit as a sign of his seriousness about the cause, and on Friday, he abruptly amended the timing of his stop to be near the conference's more pivotal end, not its beginning, to give momentum to a political deal.

The political realities back home have forced Obama to head to Denmark with only a provisional target for reducing heat-trapping gases, and to take steps at home to curb global warming that do not require Congress.

Obama has done more on his own than any other president to address climate change, even though he has stated repeatedly that a new law is the best way to handle the problem.

Billions of dollars of economic stimulus dollars have gone toward developing cleaner sources of energy. The administration is drafting the first greenhouse gas standards for automobiles and is poised to start regulating heat-trapping pollution from power plants and other large industrial facilities under existing law.

"It is as far as he can reasonably go at this stage," said Eileen Claussen, executive director of the Pew Center for Global Climate Change, an advocacy group that a year ago predicted a bill wouldn't pass by the Copenhagen conference. "While this may be disappointing to some who thought everything could be accomplished this December, I think it's better to be realistic about it."

The actions so far, widely viewed as a way to pressure Congress, have made some lawmakers more skittish and helped deepen the partisan rift.

Two Senate committees have approved parts of what may be in a final bill. But one of them, the Senate Environment and Public Works Committee, did so without any Republicans present. That was cited by backers of cap-and-trade as a sign of moving forward. Yet even some moderate Democrats viewed it as a bad way to start the debate.

"The questions is whether, as the economy improves and health care resolves, there is an effective effort by the administration to overcome partisan gridlock on climate," said Jason S. Grumet, president of the Bipartisan Policy Center and an environmental and energy adviser to Obama during the campaign.

The emission reductions Obama will propose at the U.N. conference — a 17 percent cut from 2005 levels by 2020 — probably are not achievable in the U.S. without a new law to curb heat-trapping pollution, placing more pressure on Congress to pass a bill in 2010. That's when international leaders would like to convert the political agreement they hope to get in Copenhagen into a binding treaty.

The Senate would have to ratify any treaty agreed to by the U.S.

The House in June passed a bill with the 17 percent target. Few Republicans joined in, and some Democrats who voted for it said they would work to lower the number as it made its way through the Senate.

But progress in the Senate quickly slowed as it concentrated on health care.

"Health care literally has squeezed out a huge amount of legislative effort here in Washington," said Sen. John Kerry, the Massachusetts Democrat and lead author of the Senate climate bill. Kerry is working with Republicans to find a way to broaden the legislation so it gets the 60 votes next year.

"There are definite Republican votes for this legislation right now and we hope to grow that over the course of the next weeks, months," Kerry said.

Even if Obama and Democrats eventually pass legislation, the target for 2020 is lower than what European leaders want and what scientists say is needed to avert the worst consequences of climate change.