BETHESDA, Md. (AP) — Declaring the "fight is nowhere close to being over," President Barack Obama on Tuesday heralded strides in the effort to confront Ebola in West Africa and in protecting the U.S. against the spread of the deadly virus. He said squelching the disease remains an urgent priority even if the American public's attention has shifted elsewhere.

"We cannot let down our guard, even for minute," Obama said. "We can't just fight this epidemic, we have to extinguish it."

Obama spoke after touring the National Institutes of Health in Washington's Maryland suburbs where he witnessed advances in Ebola-fighting research. He highlighted the NIH's progress in developing an Ebola vaccine, calling the initial results "exciting" while cautioning that there are "no guarantees" about the vaccine's ultimate success.

NIH researchers last week reported that the first safety study of a vaccine candidate found no serious side effects, and that it triggered signs of immune protection in 20 volunteers. U.S. health officials are planning much larger studies in West Africa to try to determine if the shots really work.

"No potential Ebola vaccine has ever made it this far," Obama said.

He prodded Congress to approve his request for $6.2 billion in emergency spending against the outbreak, urging lawmakers to act before they break for the holidays.

"We can't beat Ebola without more funding," he said. "It's a good Christmas present to the American people and to the world."

The public attention to Ebola by the president comes as Congress is assembling a massive spending bill to keep the government operating. But the legislation has become entangled with Obama's executive actions on immigration, which Republicans want to block.

Any final spending bill is expected to contain a pared down version of Obama's Ebola request. Obama asked for $2 billion for the United States Agency for International Development, $2.4 billion for the Department of Health and Human Services, and more than $1.5 billion for a contingency fund, the first item that lawmakers would likely trim.

The White House said Tuesday that Ebola Response Coordinator Ron Klain, in an update to Obama, reported that the U.S. is better prepared to deal with Ebola at home and that administration efforts to confront the virus in Liberia, Guinea and Sierra Leone are further along than two months ago.

Obama called attention to the administration's announcement Tuesday that it has set up a network of 35 hospitals across the country to deal with Ebola patients. It also said that the number of labs that can test for Ebola has increased from 13 in 13 states in August to 42 labs in 36 states.

The White House said the administration has also increased the deployment of civilians and military personnel in West Africa, bumping the U.S. presence to about 200 civilians and 3,000 troops. It said the U.S. has opened three Ebola treatment units and a hospital in Liberia.

The upbeat White House report contrasts with an assessment from Doctors Without Borders, which said Tuesday that the international response to the Ebola crisis in West Africa has been slow and uneven. It said the international community has for the most part concentrated on building Ebola management structures, but most of the hands-on work is being done by local people, national governments and non-governmental organizations.

Obama stressed the role of science while praising the medical advances against the disease, a not-too subtle rebuke of what the White House maintained was over-reaction by some politicians to the threat of Ebola in the United States.

"The basic concept of science, and making judgments on the basis of evidence, that's what's most needed during difficult, challenging moments like the ones that we had this summer and that we continue to have in West Africa," he said.

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Associated Press Medical Writer Lauran Neergaard contributed to this article.