But the signs of progress come with substantial caveats. Mr. Obama’s advisers say Ebola will remain a concern until the virus is stamped out, and public health officials are not close to achieving that goal. There has been a slight increase in cases in Guinea over the past several weeks, and in Sierra Leone the steep decline in cases has leveled off, indicating challenges in containing the disease there.

The administration plans to shift its focus from procedures like isolating patients and carrying out safe burial practices. Instead, it will step up efforts to track patients and their contacts on a case-by-case basis, officials said.

The 100 troops who will remain in Liberia will maintain the American-built health care centers as a safeguard should a sudden resurgence of the virus require United States forces to return quickly — a development that an official said the administration believed was “extremely unlikely.” The military will also leave behind some equipment, such as testing laboratories, that were monitored by military personnel, with the remaining troops training Liberians to operate them.

In addition, the United States is financing the current response effort in West Africa, which includes 2,000 “disease detectives” who are in charge of tracing new Ebola patients’ contacts, with the goal of eradicating the disease.

It is not clear how the administration will ensure that the 15 Ebola treatment centers in Liberia, the last of which was completed just last month, will remain available to patients in the event of a flare-up. Some of the facilities will be maintained at least through the end of the rainy season in October, an official said, while others will be transformed into preventive-care centers.

Mr. Obama, who won bipartisan support late last year for his $6 billion emergency financing request in the fight against Ebola, does not plan to request any new money for the effort, officials said. About $2.5 billion is financing Ebola response efforts overseas. Roughly $3 billion is dedicated to United States efforts to better confront Ebola and other infectious disease outbreaks.