The United States Secretary of State Antony Blinken has confirmed that some Americans, who wanted to leave Afghanistan, still remain in the country despite the US ending its evacuation missions on Monday.

Blinken said that the number of American citizens left is "under 200" and may well be "closer to 100". He added that the United States would work with Afghanistan’s neighbors to secure their departure either overland or by charter flight once the Kabul airport re-opens.

Speaking shortly after the Pentagon announced the completion of the US military pullout on Monday, Blinken also announced that the country's embassy in Kabul will remain closed and unmanned for the foreseeable future, the Associated Press reported.

He said that the American diplomats who had worked from the now-closed embassy will be based in Doha, Qatar.

Blinken went on to warn the Taliban that the US is not going to easily recoganise their authority over Afghanistan. 

"The Taliban have to earn their legitimacy," Blinken said, according to AFP.

Earlier on Monday, United States Central Command head General Frank McKenzie had said in a statement that the Taliban was "significantly helpful" in enabling the evacuation of Americans, Afghans, and others.

In a news conference hosted by the United States Department of Defense, McKenzie said that the Taliban is likely to face difficulty in maintaining control of Afghanistan's national capital Kabul in the coming days. The statement was made while the threat of the Islamic State, a group considered to be a nemesis of the Taliban, has carried out multiple attacks in the last week.

McKenzie says Taliban fighters in recent days have freed IS fighters from prisons, swelling their ranks to an estimated 2,000. In his words, “Now they are going to be able to reap what they sowed", according to reports from Associated Press.