GLASGOW—U.S. local weather envoy John Kerry served earn help at the United Nations summit for a offer this weekend that aims to accelerate emissions-cutting plans and asks countries to bolster them yet again subsequent 12 months.

Hours later, Mr. Kerry underscored the basic weak spot of the new agreement when he mentioned the U.S., the world’s 2nd-biggest greenhouse-fuel emitter, is not likely to pace up its have reduction program in a year’s time, arguing that it goes considerably adequate.