After WHO declared Ebola an international health emergency in August, UN Secretary-General Ban Ki-moon stepped in and had the United Nations take overall responsibility for fighting the virus.
WHO declined to comment on the document, which was not issued publicly, and said that Chan would be unavailable for an interview. She said she "was not fully informed of the evolution of the outbreak. We responded, but our response may not have matched the scale of the outbreak and the complexity of the outbreak."
Meanwhile, President Barack Obama moved to step up the US response to the disease, naming Ron Klain, a former chief-of-staff to Vice President Joe Biden, as the administration's point man on Ebola.
The White House said he would serve as "Ebola response coordinator," suggesting his key role will be to synchronise the government agenciesfighting the disease.
"This is much broader than a medical response," White House spokesman Josh Earnest said.
US officials have moved to cut off potential routes of infection from three cases in Texas, reaching a cruise ship in the Caribbean and multiple domestic airline flights.
Republican lawmakers and the Obama administration debated the value of restricting travellers from entering the US from countries where the outbreak began.
Protests outside the White House demanded an end to flights but White House, press secretary Josh Earnest said a travel ban was not under consideration. He suggested it could actually make things worse by giving people an incentive to "go underground," evade screening and conceal their travel history.
"And that means it would be much harder for us to keep tabs on these individuals and make sure that they get the screening that's needed," he said.
Other nations have taken steps to prevent travellers from the affected areas from crossing their borders. The Central American nation of Belize announced that it would immediately stop issuing visas to people from West African countries where Ebola had spread.
US officials continued their efforts to contain the fallout from the nation's first reported case of Ebola, Thomas Eric Duncan, a Liberian traveller who died last week at a Dallas hospital.
Officials said they were working to remove a hospital worker who had handled an Ebola lab specimen from a Caribbean cruise ship, although she had gone 19 days without showing any sign of infection. The Carnival Cruise Lines ship was headed back to Galveston, Texas, on Friday after failing to get clearance to dock in Cozumel, Mexico, and officials in Belize would not allow the woman to leave the ship.
The lab worker and her spouse were in isolation and she is "not deemed to be a risk to any guests or crew", a cruise line spokeswoman said.
Doctors at the National Institutes of Health in Maryland said that a Dallas nurse, Nina Pham, brought there for Ebola treatment was very tired but resting comfortably Friday in fair condition.
"We fully intend to have this patient walk out of this hospital," Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases said.
Another nurse to contract Ebola, Amber Vinson, was being treated at Emory University Hospital in Atlanta. Her uncle and family spokesman, Lawrence Vinson, said she was stable.
"She followed all of the protocols necessary when treating a patient in Dallas, and right now, she's trusting in her doctors and nurses as she is now the patient," he said.
As of October 14, 4555 people have died from Ebola out of a total of 9216 cases registered in seven countries, the WHO says. Most of the dead are in the West African nations of Guinea, Liberia and Sierra Leone.
- AAP
