Dr. Kent Brantly

WASHINGTON — 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.

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.

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 it needed to be put into action immediately — and that other countries must follow suit.

“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.