Mohammad Suhail Shaheen made the remarks in an exclusive interview with CGTN.
He spoke ahead of the G7's virtual meeting which is reported to consider an extension of the deal and whether new sanctions should be imposed on the Taliban.
Shaheen said that any delays in the withdrawal of foreign troops would only work to disrupt reconstruction plans. The Taliban was keen to bring an end to foreign troops' occupation of the country, he said.
In case of a violation, Shaheen said it was up to the movement's leadership "to decide how to proceed and what to do," and he urged the US "to participate in the reconstruction of Afghanistan because they were involved in the destruction of Afghanistan."
Asked if the Taliban will consider an extension, Shaheen said "the occupation must come to an end" and that the Taliban welcomes the US's participation in reconstruction and investment in the country.
"If they want, they can participate in the reconstruction of Afghanistan, and they can have cooperation with Afghanistan, with the people of Afghanistan in a new chapter, in a new phase," he said.
As for possible sanctions against the Taliban, Shaheen said more sanctions would be a "biased decision."
"It will be against the people of Afghanistan. The people of Afghanistan fought for 20 years against the occupation. It was a popular uprising," he said.
"We entered a new phase – a phase of peace, of peaceful coexistence, national unity of the Afghan people. So, there is a need for a lot of cooperation, financial support in this critical time."
Regarding negotiations on forming a new government, Shaheen said, "The key issues are that we have all Afghan politicians, Afghan personalities to be part of the future Afghan inclusive government."
RHM/PR