US President Barack Obama delivers remarks about the progress made to date in the response to the Ebola outbreak in West Africa, from the Eisenhower Executive Office Building on the White House campus in Washington, Feb 11, 2015. [Photo/Agencies]

WASHINGTON - US President Barack Obama heralded a "new phase in the fight" against Ebola on Wednesday and said progress against the outbreak in West Africa will allow the US to withdraw nearly all American troops sent to Liberia last fall.

He cautioned 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."

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 US civilians.

Obama's upbeat announcement, made with military responders and Ebola survivors at his side, was a significant turnabout from last year when the White House's initial response to the outbreak was criticized as inept and too slow.

Back then, 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 US tightened policies at home and dedicated more resources to West Africa.

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

Earlier on 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 US and elsewhere beyond West Africa.

The US pullout comes as Ron Klain, who led Obama's Ebola response, wraps up his short-term assignment.