Media playback is unsupported on your device Media caption Ebola nurse Kaci Hickox: "I'm free to go on a bike ride in my home town"

The governor of Maine has vowed to exercise the "full extent" of his authority to quarantine a nurse who treated Ebola patients in Africa.

Paul LePage said negotiations with Kaci Hickox, who went for a bike ride on Thursday morning, had broken down.

Her lawyers said they had not yet been served by a court order to enforce the 21-day quarantine but would fight it.

Nearly 5,000 people have died of Ebola, but only nine patients have been treated for the virus on US soil.

More than 13,700 people have been infected in total, the vast majority in the West African countries of Liberia, Sierra Leone and Guinea.

Ebola, which is only spread through close contact with the bodily fluids of a sick patient, has an incubation period of up to 21 days.

People are not infectious until they show symptoms, usually a fever.

In other developments:

a UK ship has arrived in Sierra Leone carrying food, medical equipment and 32 pick-up trucks, to help keep hard-pressed Ebola treatment centres in operation

speaking in Brussels after a trip to West Africa, US Ambassador to the UN Samantha Power has said the world must do more to confront "the greatest public health crisis ever"

North Korea has instituted a 21-day quarantine for any foreign national arriving from any country

the World Bank said it would immediately provide $100m to fund the deployment of more health workers to West Africa

US officials are at odds over whether American healthcare workers who return from treating Ebola patients in West Africa should be forced into quarantine.

One of these workers, Dr Craig Spencer, travelled around New York City before he fell ill. He is currently in isolation in hospital.

Deaths from Ebola

After his case was announced, New York, New Jersey and other states ordered the mandatory quarantine of healthcare workers who had been exposed to Ebola patients.

But President Barack Obama has warned that overly restrictive measures could discourage volunteering in West Africa.

Governor LePage said the state was willing to agree to arrangements that would have allowed Hickox to go for walks, runs and bicycle rides.

Image copyright Reuters Image caption Samantha Power (right) met Ebola survivors in Guinea

But she would be prevented from going into public places or coming within three feet (less than a metre) of other people.

But the governor said discussions with Ms Hickox, 33, had failed.

His office did not disclose what steps it would take to force her compliance, but said, "Maine statutes provide robust authority to the state to use legal measures to address threats to public health".

Ebola cases outside West Africa

Ms Hickox returned to the US on Friday, landing at Newark International Airport and immediately placed in an isolation tent outside a local hospital.

After showing no fever or other symptoms for a 24-hour period, she was discharged and brought to Maine, where she lives in a house in a rural area.

On Thursday morning, Ms Hickox left her home on a bicycle, followed by police officers who monitored her movements but who are unable to detain her until they have a court order.

UN Secretary-General Ban Ki-moon has condemned the actions of US states ordering medics to be isolated.

"Returning health workers are exceptional people who are giving of themselves for humanity," he said.

"They should not be subjected to restrictions that are not based on science."