The US special envoy who brokered a deal with the Taliban called Sunday for the insurgents to implement a humanitarian ceasefire while Afghanistan tries to tackle its worsening coronavirus crisis.

In a series of tweets marking the start of the Islamic holy month of Ramadan, Zalmay Khalilzad said all sides should focus on fighting a "shared enemy".

"The well-being of the Afghan people and the country itself depend on all parties devoting their full energies to the fight against the COVID-19 pandemic," the Afghanistan-born US negotiator said.

"Ramadan offers the Taliban an opportunity to embrace a humanitarian ceasefire to reduce violence and suspend offensive military operations until the health crisis is over."