Copenhagen ? U.N. climate negotiators looked Wednesday to the United States to bring fresh ideas — perhaps in the form of extra billions of dollars — to try to salvage a bare-bones political agreement by the end of the week on controlling global warming.

The U.S. must find ways of meeting demands by a suspicious world on reducing greenhouse gas emissions without exceeding what Congress will allow. It must also find the cash in a tight budget.

“The United States is back and President Barack Obama is coming to Copenhagen to put America on the right side of history,” said Sen. John Kerry, chairman of the Senate Foreign Relations Committee.

Secretary of State Hillary Rodham Clinton was on her way to Copenhagen as negotiations over a draft agreement effectively came to a halt after an all-night session that broke up at dawn Wednesday with a confused text leaving most issues to be decided by ministers or heads of government. Obama is scheduled to arrive Friday.

Left unresolved are the questions of emissions targets for industrial countries, billions of dollars a year in funding for poor countries to contend with climate change, and verifying the actions of emerging powers like China and India to ensure that promises to reduce emissions are kept.

Denmark, presiding at the conference, said it has drawn up a text that it would present when ministers resume talks, but delegates were undecided on the format to hold the negotiations, whether in a full plenary or in small groups.

Formal discussions were suspended before resuming at 10 p.m. local time, met briefly, then adjourned for the night.

“I still believe it’s possible to reach a real success,” said the U.N.’s top climate official, Yvo de Boer. “The next 24 hours are absolutely crucial and need to be used productively.”

British Climate Change Secretary Ed Miliband told the BBC that the climate change talks were “certainly on a knife edge and in real grave danger. … It now needs leaders, unfortunately, to come in and move this process forward.”

The U.S. delegation objected to a proposed text it felt might bind Washington prematurely to reducing greenhouse gas emissions before Congress acts on the required legislation. U.S. envoys insisted, for example, on replacing the word “shall” with the conditional “should” throughout the text.

Veterans of these conferences said such stalls were not unusual. “I know that often negotiations reach the halfway point about an hour before an agreement,” said Jennifer Haverkamp, a former trade negotiator and a climate analyst for the Environmental Defense Fund.

In one sign of progress, six countries pledged a total of $3.5 billion over three years — $1 billion from the U.S. — to protect the world’s forests. It will be channeled to developing countries that produce plans to slow and eventually reverse deforestation.

But that was just a fraction of a U.N.-proposed three-year package of at least $30 billion for poor countries to prepare defenses against rising seas, drought and other severe effects of global warming, including economic and physical security.

Japan said it would it would contribute half the needed funds, $15 billion, in public and private finance, “on condition that successful political accord is achieved” in Copenhagen.

Among Clinton’s first scheduled meetings today is a private talk with China, America’s protagonist in a dispute over whether developing countries will be required to report and verify their actions to reduce emissions.