An American doctor who survived Ebola said there's no time to waste as President Barack Obama outlined his plan to ramp up the U.S. response to the epidemic in West Africa.

"We can't afford to wait months, or even weeks, to take action, to put people on the ground," Dr. Kent Brantly told senators Tuesday.

Obama called the Ebola crisis a threat to world security as he ordered up to 3,000 U.S. military personnel to the region along with an aggressive effort to train health care workers and deliver field hospitals. Under the plan, the government could end up devoting $1 billion to containing the disease.

"If the outbreak is not stopped now, we could be looking at hundreds of thousands of people affected, with profound economic, political and security implications for all of us," Obama said after briefings in Atlanta with doctors from the Centers for Disease Control and Prevention and from Emory University, where Brantly and two other aid workers with Ebola have been treated.

President Obama met today with Dr. Kent Brantly, an Ebola survivor who contracted the virus while doing... http://t.co/cmQUsrDXgV — US Consulate Thess (@USConsulateThes) September 17, 2014

Obama acted under pressure from regional leaders and international aid organizations who pleaded for a heightened U.S. role in confronting the deadly virus. He called on other countries to also quickly supply more health workers, equipment and money.

"It's a potential threat to global security if these countries break down," Obama said, speaking of the hardest-hit countries of Liberia, Sierra Leone and Guinea. At least 2,400 people have died, with Liberia bearing the brunt.

He described the task ahead as "daunting" but said what gives him hope is that "the world knows how to fight this disease."

Topping the new aid, the U.S. promises to deliver 17 100-bed treatment centers to Liberia, where contagious patients often sit in the streets, turned away from packed Ebola units. The Pentagon expects to have the first treatment units open within a few weeks, part of a heightened U.S. response that includes training more local health care workers.

"This massive ramp-up of support from the United States is precisely the kind of transformational change we need to get a grip on the outbreak and begin to turn it around," said World Health Organization Director-General Margaret Chan.

Doctors Without Borders, which has sounded the alarm for months, also welcomed the U.S. scale-up but said that it needed to be put into action immediately — and that other countries must follow suit.

Dr. Kent Brantly, Ebola survivor, gave testimony at Senate yesterday. Here's his speech. http://t.co/Bx4pXXviZy — Nonya Bidniss (@nonya_bidniss) September 17, 2014

"The response to Ebola continues to fall dangerously behind and too many lives are being lost," said Brice de le Vingne, the group's director of operations. "We need more countries to stand up, we need greater concrete action on the ground, and we need it now."

Nearly 5,000 people have become ill from Ebola in Liberia, Sierra Leone, Guinea, Nigeria and Senegal since it was first recognized in March. WHO says it anticipates that figure could rise to more than 20,000 and end up costing nearly $1 billion to contain.

The U.N. Security Council will hold an emergency meeting Thursday on the crisis, and the head of the United Nations said the General Assembly will follow up with a high-level meeting next week as the world body "is taking the lead now" on the international fight.

U.N. Secretary-General Ban Ki-moon welcomed Obama's plan, his spokesman said in a statement, and called on the international community "to be as bold and courageous in its response as those who are on the front lines fighting this disease."

At a packed Senate hearing, the CDC's Dr. Beth Bell told senators the outbreak is "ferocious and spreading exponentially."

"If we do not act now to stop Ebola, we could be dealing with it for years to come," she warned.

Congress still must vote on an Obama administration request for $88 million more to help the Ebola fight, including funding CDC work in West Africa through December and speeding development of experimental treatments and vaccines.

The U.S. already has spent more than $100 million fighting the outbreak. Obama administration officials said some of the costs of the new military response would be covered by $500 million in overseas contingency operations, such as the war in Afghanistan, that the Pentagon already has asked Congress to redirect for West Africa and for humanitarian assistance in Iraq. Late Tuesday, the Obama administration submitted a request to reprogram another $500 million in Pentagon money for the Ebola effort.

Sen. Lamar Alexander, R-Tenn., said urgent action was needed. "We must take the dangerous, deadly threat of the Ebola epidemic as seriously as we take ISIS," he said, referring to the extremist group in Syria and Iraq.

White House press secretary Josh Earnest said the 3,000 troops would not provide direct care to Ebola patients. In addition to delivering the 17 treatment facilities, they will help train as many as 500 local health care workers a week. Among other initiatives the military will:

—Set up a headquarters in Monrovia, Liberia, led by Maj. Gen. Darryl Williams, head of U.S. Army Africa.

—Build a regional transportation and staging base in Senegal, where the U.S. will help coordinate the contributions of other allies and partners.

—Provide home health care kits to hundreds of thousands of households, designed to help healthy people caring for Ebola-stricken family members. That includes 50,000 kits the U.S. Agency for International Development will deliver to Liberia this week.

—Carrying out a home- and community-based campaign to train local populations on how to handle exposed patients.

In Monrovia, Boima Folley runs a sport materials shop and said he'd welcome the U.S. military response.

"We have been praying to get the disease wiped out of our country, so if the coming of U.S. troops will help us get that done, we should be happy," he said.

"The soldiers don't have to have medical backgrounds. They can help with logistics," he added.

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