Marcia Bernicat, the principal deputy assistant secretary of state for oceans and international environmental and scientific affairs, "will represent the United States at the UN Secretary General's Climate Summit," a State Department spokeswoman said.
President Donald Trump is expected to be in New York, where he lives within walking distance of the United Nations, when the summit opens Monday.
But his administration is skeptical of action on climate change as well as international organizations, often mocking global meetings as feel-good events devoid of action.
Trump pulled the United States out of the Paris climate accord, calling it unfair to business, and just Wednesday revoked California's authority to set tougher limits on auto emissions.
Guterres has called on UN leaders to meet on climate change ahead of the annual General Assembly to redouble efforts to check global warming at no more than 1.5 to 2 degrees Celsius above pre-industrial levels.
With temperatures already on course to exceed that range, a recent report by a global commission warned that climate change could push more than 100 million people in the developing world below the poverty line.