Mr. Obama is expected to detail the plan during a visit Tuesday to the Centers for Disease Control and Prevention in Atlanta, these people said. Among the possible moves: sending additional portable hospitals, doctors and health-care experts, providing medical supplies and conducting training for health workers in Liberia and other countries.

Mr. Obama also is expected to urge Congress to approve the request he made last week for an additional $88 million to fund his proposal.

“There’s a lot that we’ve been putting toward this, but it is not sufficient,” Lisa Monaco, Mr. Obama’s counterterrorism adviser, said in an interview Sunday. “So the president has directed a more scaled-up response and that’s what you’re going to hear more about on Tuesday.”