The U.N.'s top climate official says emissions-cutting pledges made by governments ahead of a December conference are a good step toward achieving an international global-warming goal, but they aren't yet enough.

Christiana Figueres made clear Friday that plans submitted by 146 countries for the climate conference in Paris won't be the last word. She says "many countries have been healthily conservative in what they have put on the table" and "do not want to expose themselves prematurely."

The international goal is to keep global temperatures from increasing more than 2 degrees Celsius (3.6 degrees Fahrenheit) by the end of the century. Friday's U.N. report directly assessed only the plans' shorter-term impact, but Figueres cited an International Energy Agency assessment that they could keep the temperature rise to 2.7 degrees.