President Obama said Wednesday that progress against the Ebola outbreak in West Africa will allow the U.S. to withdraw nearly all American troops sent to Liberia last fall.

But he said the mission was not over, and he set an ambitious goal of eliminating the disease.

"We have risen to the challenge," he said at the White House. "Our focus now is getting to zero."

Surrounded by military responders and Ebola survivors, the president heralded a "new phase in the fight" against Ebola.

Obama said only 100 of the 2,800 troops sent to Liberia will remain there after April 30. About 1,500 have returned home. Those staying will work with Liberia's military, regional partners and U.S. civilians.

Earlier Wednesday, he met with philanthropists and foundation leaders who had supported the fight against the outbreak, which had threatened to spiral out of control and fostered fears in the U.S. and elsewhere beyond West Africa.

Obama's announcement was a welcome development at the White House, whose initial response last year was criticized as inept and too slow.

Obama resisted calls to impose a travel ban and was forced to cancel midterm campaign appearances to stay in Washington and focus on Ebola, particularly after health workers contracted the virus at a Texas hospital while treating a man who was infected in Africa.

The U.S. tightened policies at home and dedicated more resources to West Africa.

"People were understandably afraid," Obama said. "Some stoked those fears."