he United States will keep a pledge to cut greenhouse gas emissions made last year perhaps with help from a domestic boom in cleaner-burning natural gas, Washington’s lead negotiator said at the U.N. climate talks.

At last year’s climate talks in Copenhagen, U.S. President Barack Obama pledged the United States would cut emissions in a range of 17 percent below 2005 levels by 2020.

“We must stand behind the underpinnings of what our leaders agreed to last year,” Jonathan Pershing, the head of the U.S. delegation, told reporters on the first day of the annual two-week talks, held in Mexico this year.