Former British Prime Minister Tony Blair has slammed the US for an "imbecilic" decision to withdraw troops from Afghanistan in his first statement since the Taliban regained the control of the Asian country.

"The abandonment of Afghanistan and its people is tragic, dangerous, unnecessary," Blair, who took Britain into war in Afghanistan alongside the US in 2001, wrote in an article published on Saturday on the website of his Institute for Global Change, Xinhua news agency reported on Sunday.