Two Americans infected with ebola in West Africa are to be flown back to the US in the coming days, as world health officials warned the outbreak was moving too quickly.
The Pentagon confirmed on Friday that arrangements were being made for a chartered flight to land at Dobbins Air Base in Marietta, Georgia.
It is expected to transport Dr Kent Brantly, 33, and 59-year-old Nancy Writebol, a missionary.
Health workers carry an ebola victim's body in Sierra LeoneThey were said on Thursday to be in a "stable but grave condition" after contracting the haemorrhagic fever in the Liberian capital Monrovia.
The State Department said on Friday it was leading preparations to evacuate the two Americans back to the US to be cared for in strict isolation.
Spokeswoman Marie Harf said the patients, whom she declined to identify citing privacy concerns, would be taken to medical facilities with appropriate isolation and treatment capabilities.
The patients will be transported in a specially designed portable tentEmory University Hospital, in southern Georgia, said it was preparing to accept two ebola patients to its containment unit within the next several days.
A small private jet was dispatched from the US state of Georgia to Liberia on Thursday.
The aircraft has been fitted with a portable tent designed for transporting patients with highly infectious diseases, AP news agency reports.
A modified Gulfstream III jet will fly the Americans back to GeorgiaThe World Health Organisation's director-general warned on Friday that the ebola outbreak, which has killed at least 729 people, is out of control but can be stopped.
Margaret Chan told the presidents of Guinea, Liberia and Sierra, the three worst affected nations: "This outbreak is moving faster than our efforts to control it.
"If the situation continues to deteriorate, the consequences can be catastrophic in terms of lost lives but also severe socioeconomic disruption and a high risk of spread to other countries.
Emory University Hospital in Atlanta has a dedicated containment unit"This meeting must mark a turning point in the outbreak response."
Guinea, Liberia and Sierra Leone announced on Friday a quarantine zone to seal off the epicentre of the outbreak where the three countries meet.
One US citizen has already died of the virus. Liberian health ministry official Patrick Sawyer, a naturalised American, began vomiting on a flight from Liberia to Nigeria last month.
Medical staff take a blood sample from an ebola patient in Sierra LeoneMr Sawyer, who had planned to visit family in Minnesota in August, was taken to a hospital in Lagos where he died.
His case sparked particular alarm because he was able to board an international flight while infected with the incurable disease.
Two other Americans - Peace Corps volunteers - have been isolated after becoming exposed to ebola in West Africa and are under observation, though neither has shown any symptoms.