WASHINGTON - U.N. Secretary-General Ban Ki-moon pressed the Senate Tuesday to take action on climate change, but key senators made it clear that a bill is unlikely to pass this year.

The U.N. chief met with members of the Senate Foreign Relations Committee late Tuesday afternoon to discuss the status of negotiations on a new international pact to slow global warming before 192 nations meet in Copenhagen next month. The meeting came a day after President Barack Obama said he was willing to go to Copenhagen if his presence would help clinch a deal.

Ban told the senators it was critical for the U.S. to take the lead, but he also said he understood that the Senate may not be in a position to take concrete action before the talks.

"From what I heard today, there is great support in the Senate for action on climate change," Ban said. "I would sincerely hope that the Senate would take necessary action as soon as possible."

But just how soon the U.S. Senate will act on climate change is uncertain. Leading senators made it clear Tuesday that a bill was unlikely to reach the Senate floor by the end of the year. The House narrowly passed its version of a global warming bill in June.

At the same time, Ban and Janos Pasztor, the director of his Climate Change Support Team, have scaled back their expectations for a new international treaty in Copenhagen. In the past month, they have focused instead on getting a political deal on the basic elements that can be turned into a treaty, hopefully next year.

Sen. John Kerry, D-Mass., the author of the Senate bill that would set the first-ever U.S. limits on greenhouse gases, said Tuesday that he hoped to have an outline of where the Senate was headed by the time of the Copenhagen meeting. Kerry, along with Sen. Lindsey Graham, R-S.C., and Sen. Joe Lieberman, I-Conn., are working to piece together a bill that can get the 60 votes needed to pass the Senate.

Kerry's bill last week was voted out of a Senate panel, sidestepping a Republican boycott. But five other committees will also have a say in the legislation.

On Tuesday, Kerry said that the bill would come to the floor "as soon as practical" and he was confident that when it did, the U.S. Senate would do its part.

Lieberman said he expects debate before the full Senate to begin early next year.

"But we will go to Copenhagen with a House-passed climate change bill, some momentum in the Senate ... and the Obama administration clearly supportive of climate change legislation," Lieberman said.

Ban acknowledged that some senators had lingering concerns about the costs associated with limiting the gases blamed for global warming and whether other countries will do their share to control emissions.

He responded to those criticisms by saying that the cost of inaction was far greater, and that other countries are already moving down a pathway to cleaner sources of energy.

"I also told the Senate that the world is not standing still," Ban said.