David Jackson and Liz Szabo

USA TODAY

Calling Ebola a threat to both global health and national security, President Obama said Tuesday he is sending 3,000 troops to West Africa to help contain the deadly virus and prevent it from spreading to the United States and across the globe.

"If the outbreak is not stopped now, we could be looking at hundreds of thousands of people infected, with profound political and economic and security implications for all of us," Obama said.

Proclaiming that "we have to act fast — we can't dawdle on this one," Obama said that "this is a global threat, and it demands a truly global response."

While the disease is "spiraling out of control" in West Africa, Obama said the chances of an Ebola outbreak in the United States are "extremely low" and will stay that way if the United States acts.

The plan he outlined calls for more doctors and health care professionals; more portable hospitals, laboratories, and other medical facilities; and increased training for first responders and other medical officials throughout West Africa.

"The world knows how to fight this disease," Obama said. "It's not a mystery. We know the science."

Officials and citizens in Africa and throughout the globe welcomed the administration's plan, though some called it tardy and questioned whether it would be comprehensive enough to contain the virus.

The total cost of the administration's Ebola program is estimated at up to $1.26 billion, officials said, including $175 million that has already been dedicated to fight the disease that has claimed more than 2,400 lives in Africa.

The Department of Defense, which is heading up the program, has requested the re-programming of $1 billion, officials said. The administration has asked Congress for an additional $88 million for the anti-Ebola program.

The plan has four general goals, Obama said: to control the Ebola outbreak, prevent "ripple effects" that could lead to economic and humanitarian disasters, coordinate a global response, and build up Africa's public health care system.

"It's a potential threat to global security if these countries break down," Obama said, referring in particular to the hardest-hit countries of Liberia, Sierra Leone and Guinea.

Obama reported that he met at the White House on Tuesday with Kent Brantly, an American doctor who contracted Ebola while working in Africa and survived after treatment in the United States.

The troops to be dispatched to Africa will not be providing "direct patient care," White House spokesman Josh Earnest said, but instead provide logistical and engineering support to health care professionals. Earnest said the involvement of the U.S. military should give people confidence in the plan, both in Africa and worldwide.

The World Health Organization is reporting more than 5,000 overall cases in West Africa, including more than 2,500 deaths from the virus that causes high fevers and uncontrolled bleeding.

Public health officials tentatively praised the plan, though some said more resources may needed to contain the Ebola virus.

Daniel Lucey, a doctor who treated Ebola patients in Sierra Leone for three weeks in August, described the administration's plan as an "essential first step" in a long journey.

"There is no guarantee of success, but there would be a guarantee of failure if Obama hadn't announced this plan," said Lucey, an adjunct professor of microbiology and immunology at Georgetown University Medical Center.

Will it be enough? Ken Isaacs, vice president of programs and government relations at Samaritan's Purse, a missionary group that has run an Ebola treatment center in Liberia, said the number of Ebola patients has doubled in just the past month. If cases continue to double every three weeks, as some predict, the outbreak could affect 100,000 people, or even 250,000.

"There simply aren't going to be enough beds," Isaacs said.

Isaacs said his organization will train people to treat family members with Ebola at home. That is also a component of the U.S. plan, officials said.

The global response to the Ebola outbreak in West Africa to date has been widely viewed an ineffective and uncoordinated. The United States will have to work closely with other countries, from those directed affected by Ebola to nations such as Cuba and China, which are also sending health workers to Africa.

It needs to be "very clear who reports to whom and what needs to be done," Lucey said, adding that the United States and the world are facing a different kind of Ebola outbreak from those in the past.

"This is urban Ebola," Lucey said. "It's unprecedented and it's uncontrolled."

Citizens in West Africa, where governments have been requesting U.S. assistance, welcomed the Obama administration's announcement.

"When I read that the Americans were coming to help stop the outbreak, I was very pleased, even if it is coming very late," said Guelor Djoe, a 28-year-old university student in Dakar, Senegal. "Ebola is ravaging these countries and I think it's time the Americans sent materials and manpower."

Ibrahim Moiwo, 45, a mechanic in Freetown, Sierra Leone, said "no support is too small," and that Ebola "is gradually destroying our country."

The goals of the Obama plan include the training of up to 500 health care workers a week and construction of up to 17 health care facilities of 100 beds each. Home health care kits will be distributed, and local populations will be trained on how to handle suddenly infected Ebola patients.

The military will help coordinate the project through a joint command headquarters in Monrovia, Liberia, one of the countries hardest hit by the Ebola outbreak.

The effort has been dubbed Operation United Assistance, in concert with governments in Guinea, Liberia, Sierra Leone, Nigeria, and Senegal. The Department of Defense will work with the United States Agency for International Development and the Centers for Disease Control.

Dr. Jesse Goodman, an infectious disease specialist and professor of medicine at Georgetown University Medical Center, said it's important that the African nations are encouraging the U.S. mission.

The epidemic was caused in part by mistrust of government, Goodman said, leading people to avoid treatment centers and hide their disease. Winning the public's trust will be a "critical determinant of success" going forward, he said.

During his remarks in Atlanta, Obama said, "The scenes that we're witnessing in West Africa today are absolutely gut-wrenching." Ebola victims, he said, "are just sitting, waiting to die right now."

American officials stressed that the virus does yet not threaten the United States.

Beth Bell, director of the National Center for Emerging and Zoonotic Infectious Diseases at the CDC, said that 100 members of the CDC staff are working now in West Africa, and hundreds more are assisting from Atlanta. She said, "the best way to protect the U.S. is to stop the outbreak in West Africa."

Officials are also working to protect troops and U.S. personnel working in Africa, Bell said, and that includes training in the use of protective equipment.

"We have taken a lot of steps to do everything we can to minimize the risk, but it is a very difficult situation," she said. "This is something I worry about with my own staff every day."

While declining to discuss the plan in detail, Earnest said Obama believes that "making an investment here early is critical to trying to snuff out this problem before it becomes a much more widespread problem."

The plan won tentative backing from lawmakers in Congress.

"I support these efforts to contain the Ebola epidemic, and know that we will monitor this humanitarian crisis in the weeks ahead," said Senate Minority Leader Mitch McConnell, R-Ky.

Another Republican — Sen. Lamar Alexander of Tennessee -- said the nation needs to take Ebola as seriously as it does the threats from Islamic State militants. "The spread of this disease deserves a more urgent response than it's now getting," he said.

Senate Majority Leader Harry Reid, D-Nev., also expressed support, saying that "no one's better equipped to do something like this than the military."

Contributing: Karen Weintraub, Jennifer Lazuta, Alpha Kamara