If any Western troops stay in Afghanistan it will be considered "a continuation of the invasion", a spokesman for the Taliban has told Euronews in Kabul.
Zabihullah Mujahid was speaking ahead of August 31, the date by which President Joe Biden said the US mission to the country would end.
The Pentagon said on Sunday the remaining contingent of US forces at the airport, now numbering fewer than 4,000, had begun their final withdrawal before Tuesday.
"Any remaining military presence will be considered by Afghans as a continuation of the invasion," Mujahid told Euronews.
"Afghans are very sensitive about this issue.
"First, American forces have to retreat, secondly an Islamic government will be formed. Killing people in the name of Islam cannot be an excuse to continue the war in the country or to kill people.
"We believe, they realised the truth and the situation of the country is intense, people have no more power to fight.
"An Islamic government will be formed and Afghans will obtain their independence."
The Taliban swept to power in mid-August after a rapid takeover of the country, which culminated in President Ashraf Ghani fleeing.
The new regime -- keen to portray itself as more moderate than the one in the late 1990s when a strict form of Islamic rule was imposed -- has promised to respect women's rights and forgive those who fought against them.
But many Afghans remain sceptical and thousands have raced to the airport, desperate to flee the country.