UNITED NATIONS — Seeking to speed the response to the Ebola outbreak in West Africa, President Obama delivered a blunt warning on Thursday at a high-level United Nations meeting devoted to the health crisis: The world was doing too little and moving too slowly.

Mr. Obama cited his announcements last week that the Pentagon would build a field hospital and treatment units in Liberia, Guinea, and Sierra Leone — along with the establishment of a United Nations emergency mission to respond to the Ebola outbreak — as positive steps.

“But I want us to be clear: We are not moving fast enough. We are not doing enough,” the president said. “There is still a significant gap between where we are and where we need to be.”

Mr. Obama called on countries to supply air transportation and medical evacuation services, as well as doctors and medical equipment. The United States, he said, could build a network of treatment centers but did not have enough doctors by itself to contain the outbreak.