L'AQUILA, ITALY, AND WASHINGTON — Developing nations led by China and India refused Wednesday to back lofty but long-term targets proposed by the Group of 8 industrial nations to cut greenhouse gas emissions, balking at reluctance by leaders of the world's biggest economies to move more quickly on their own.
Inability to bridge the gap between rising carbon-emitting countries such as China and the longtime polluters within the G-8 underscores the steep challenges involved in attempting to strike a comprehensive bargain to contain global warming.
The impasse comes down to the politically sensitive issue of who goes first.
President Obama and his counterparts in the G-8, who are holding two days of meetings in the central Italian mountain town of L'Aquila, offered broad agreements to reduce greenhouse gas emissions by 2050. The statement pledged to slash global emissions by 50%, led by reductions of 80% by the G-8 countries.
They also prepared to offer new financial incentives for developing nations to join the effort.
But the G-8 stopped well short of pledging to take aggressive action that could curb emissions more quickly -- at the cost of higher energy prices and a feared worsening of the global economy.
And neither the broad promises of future action nor the relatively modest financial incentives were likely to break the standoff between the most advanced economies and the emerging powerhouses. Countries such as China, India and Brazil are unwilling to take the first steps to cut emissions that could choke off economic growth, instead demanding that wealthier nations take the lead.
"China's not going to do anything until the developed countries send a signal that they're going to do something," said Michael Oppenheimer, a geoscientist at Princeton University and a longtime participant in the Intergovernmental Panel on Climate Change.
The standoff at the summit perpetuates a divide that must be bridged this year if there is to be a global agreement on curbing emissions.
The United Nations is convening a meeting in Copenhagen in December aimed at forging a binding consensus on targets to reduce greenhouse gas emissions. But unless China and other developing nations can be persuaded to sign on to an accord, Obama may find it difficult -- if not impossible -- to convince Congress to go along.
The stalemate on the international stage mirrors Obama's problem at home. Though the House approved a major climate bill last month, Republicans and other critics have unleashed a hailstorm of criticism. They argue that emissions limits by the United States and other advanced economies alone would have relatively little effect on global warming, while potentially harming the domestic economy.
Obama's climate bill, which narrowly passed the House, could send a strong signal if it becomes law, said Dirk Forrister, who was chairman of the White House climate change task force under President Clinton and now is managing director of the financial firm Natsource LLC.
But, he said, "the U.S. Senate will not go along with anything unless it sees some pretty serious action from developing countries." That, analysts say, sums up Obama's conundrum as he tries to push for a meaningful climate agreement during formal treaty negotiations in Denmark this winter.
"It looks like it's going to be a pretty tough fight [in Copenhagen], based on what happened in these meetings in Italy," Forrister said.
U.S. leaders hinted that a broad coalition of developing and developed nations could announce agreement today to team up on research on renewable energy and technology to scrub and store greenhouse emissions from coal.
Michael Froman, Obama's point man at the summit and lead staff negotiator, argued that the major industrial nations' joint statement favoring an 80% reduction in their emissions by 2050 represented "significant cooperation" -- even though it came up short of the draft language that the White House had supported.
The G-8 targets roughly followed those in Obama's domestic climate bill.
The G-8 countries also set a global goal of 50% emissions reductions by mid-century, and declared that they recognized "the broad scientific view that the increase in global average temperature above preindustrial levels ought not to exceed" 2 degrees Celsius (3.6 degrees Fahrenheit).
They did not announce any specific plans to cut emissions or adopt any short- or mid-term reduction targets. The United States pushed, and failed, to get developing nations to join in the reduction pledge.
"In any negotiation, you put in a number of points," Froman said.
"Sometimes they make it in and sometimes they don't."
The statement that did not come -- the one that would have included China, Brazil and other developing countries -- is the one that matters, he acknowledged.
But both Froman and chief Obama climate negotiator Todd Stern argued that there was plenty of room to work out an agreement before the Copenhagen summit.
"It's a negotiation. Countries may make concessions further down the road," Stern said in an interview.
Obama will chair a meeting of the world's largest emitters, including both developing and developed nations, today in Italy.
Analysts said the Obama administration could strengthen its hand in future negotiations with another victory or two at home -- Senate approval of a climate bill and, even better, passage by Congress of a conference version of the bill that Obama could sign into law before the Copenhagen talks.
"His most powerful weapon is a piece of signed legislation," said Melinda L. Kimble, senior vice president of the United Nations Foundation and a former climate negotiator in the Clinton administration.
"If he has that in his pocket," she added, "everything else he has is icing on the cake."