(AP) -- The Obama administration on Friday urged calm over the single case of Ebola in the United States, seeking to reassure the American public that there was little chance of an outbreak of the disease in this country. The Pentagon said it had begun the long-awaited aid to disease-ravaged Liberia, with medical testing at two new labs and construction of treatment centers.

The administration has long contended that the best way to contain Ebola is to attack it at its source. The Pentagon's spokesman said Friday that up to 4,000 troops could be deployed to West Africa, a number that has been slowly climbing as military leaders arrive and assess the need.

But in the U.S., "we need to get the information out because there is a lot of fear," said Dr. Anthony Fauci, infectious diseases chief at the National Institutes of Health.

"Our health care infrastructure in the United States is well-equipped to stop Ebola in its tracks."

The unusual high-level briefing at the White House Friday reflected the administration's urgency in seeking to reassure the public that a wide-spread outbreak of Ebola in the U.S. was unlikely.

Fauci was one of five senior administration officials who briefed reporters Friday, including Health and Human Services Secretary Sylvia Mathews Burwell and Lisa Monaco, President Barack Obama's top homeland security advisers.

Monaco said the U.S. was not considering a travel ban to prevent people from the hardest-hit West African countries from coming to the U.S. and said efforts were instead focused on identify high-risk individuals before they leave the outbreak zone. Dozens and dozens of people have been stopped from getting on flights in the region, she said.

"The most effective way to go about controlling this is to prevent those individuals from getting on a plane in the first place," she said.

The first person diagnosed with Ebola in the nation went to a Dallas hospital last week but was mistakenly sent home, despite revealing he was visiting from Liberia, before returning by ambulance days later. Texas officials now are monitoring 50 people, 10 of whom they consider at high risk, who came into the contact with the man. They've had to quarantine four of them, and even had problems getting rid of the infectious waste left in the apartment where the patient stayed.

"There were things that did not go the way they should have in Dallas," acknowledged Fauci, director of NIH's National Institute for Allergy and Infectious Diseases. "But there were a lot of things that went right and are going right."

The White House said Obama planned to meet with his national security advisers Monday to discuss the Ebola outbreak and the administration's response.

Back at the Pentagon, Navy Rear Adm. John Kirby said the military has begun medical testing for Ebola at two new labs in Liberia. Also, service members are starting to build two treatment centers there for victims of the deadly disease, he said, and a hospital for infected medical personnel should be finished by the end of the month.

Kirby said that the service members are not going to treat patients and are not expected to come in contact with anyone who is infected. But he said the military is training the troops about how to avoid getting Ebola, and also setting plans in place to deal with any service member who might get infected.

"We're going to train them up on what Ebola looks like, feels like, does. While they're there, they're going to be constantly monitored on a regular, frequent basis," Kirby said. "There will be a screening process to make sure that once they're no longer there, that we're able to stay in touch with them, make sure that they haven't ... felt or experienced any symptoms."

He added that troops will also have personal protection equipment if needed and will be trained in how to use it. He said he is unaware of any special staffing or other changes at military hospitals in the United States to prepare them for caring for Ebola patients.

There are about 230 U.S. troops deployed for the Ebola mission now. About two dozen are in Senegal setting up a transportation center and the rest are in Liberia. The Army on Friday said that up to 3,200 soldiers from various units around the country will be going to Liberia, including 1,800 from Fort Campbell, Kentucky, who will arrive late this month.

Others from Fort Hood and Fort Bliss, Texas, and Fort Bragg, North Carolina, are also being deployed, along with support units from Fort Benning and Fort Stewart, Georgia, and Fort Eustis, Virginia.

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AP White House Correspondent Julie Pace contributed to this report.