WASHINGTON - The Obama administration warned yesterday that the United States could slip further behind China and other countries in development of clean energy if Congress failed to pass climate legislation, as early signs of a rift emerged among Democrats over the bill's costs.

Energy Secretary Steven Chu told a Senate panel that the United States had stumbled in the clean-energy race and that to catch up, Congress must enact comprehensive energy legislation that puts the first-ever limits on the gases blamed for global warming.

"The United States . . . has fallen behind," Chu said. "But I remain confident that we can make up the ground."

Chu was one of five administration officials to push for legislation before the Senate Environment and Public Works Committee as it opened its first debate on a 925-page bill that would reduce greenhouse gases by about 80 percent by midcentury.

While the legislation is likely to clear the environment panel, more than a dozen Democrats have voiced concerns about the potential economic fallout from shifting away from fossil fuels to reduce carbon dioxide and other greenhouse-gas emissions.

Sen. Max Baucus (D., Mont.), chairman of the Finance Committee, told the hearing he had "serious reservations" with the aggressive effort to cut emissions over the next decade. The bill for cutting greenhouse gases by 20 percent by 2020, a target that was scaled back to 17 percent in the House after opposition from coal-state Democrats.

"We cannot afford a first step that takes us further away from an achievable consensus on commonsense climate-change legislation," he said.

The chief author of the Senate bill, John Kerry (D., Mass.), acknowledged that it would raise energy prices but said the savings from reducing energy and the money to be made in new technologies were far greater. "Are there some costs? Yes, sir, there are some costs," Kerry said.

He added that while an array of studies showed restricting greenhouse gases would lead to higher energy prices, "none of them factor in the cost of doing nothing."

Kerry got some much-needed backup from President Obama, who made a stop at a solar-energy site in Florida yesterday. Obama warned that opponents, whom he did not identify, would work against the climate bill. "They're going to argue that we should do nothing, stand pat, do less, or delay action yet again," Obama said. "It's a debate between looking backward and looking forward."

An Environmental Protection Agency analysis released Friday said the average household would pay an additional $80 to $111 a year to power their homes and fuel their cars if the bill became law and businesses pass on the cost of reducing pollution to consumers.

Republicans yesterday questioned the validity of the EPA study. And Sen. James M. Inhofe of Oklahoma, the panel's top Republican, and a skeptic of the science behind global warming, said Americans would not stomach the expense. "This is something the American people can't tolerate, and I don't think they will," he said.

With just weeks remaining before 192 nations gather in Copenhagen, Denmark, to negotiate a new global treaty to slow climate change, time is running out for the Senate to bridge the differences and pass a climate bill this year.

Republicans complained that chairwoman Barbara Boxer (D., Calif.), who hopes to have the bill out of the environment committee in early November, was trying to rush the bill without proper study.

"Why are we trying to jam down this legislation now?" asked Sen. George V. Voinovich (R., Ohio). "Wouldn't it be smarter to take our time and do it right?"

The Senate bill would reduce U.S. emissions by 83 percent from 2005 levels by 2050. The bill includes financial incentives to capture and store carbon dioxide from coal burning and support for efficiency, renewable energy, and clean vehicles. It would provide assistance to steel and other industries that use large amounts of energy. The money would come from the sale of permits for pollution emissions. The largest segment of these funds - 35 percent - would go to holding down energy costs for consumers.