A repeat of the devastating Sept. 11, 2001 terrorist attacks could happen if the international community abandons Afghanistan, a peace negotiator for Afghanistan told CNBC.

The U.S. on Monday announced that the last evacuation flight had left Kabul, marking the final withdrawal of U.S. troops from Afghanistan and an end to 20 years of war.

Khalid Noor, a member of the former Afghan government’s peace negotiating team, said the world made a mistake when it abandoned Afghanistan after Soviet troops withdrew from the country in 1989.

If that happens again, terrorist groups will emerge and plan attacks around the world.

“We have said this very clearly — that the international community, if they repeat the same mistake they did in the past, that the war and … terrorism will reach their gates once again, will reach their cities once again,” said Noor, who was part of the Afghan delegation in Qatar that negotiated with the Taliban in July 2019.

“And once again, they will … witness another 9/11,” he told CNBC’s “Capital Connection” on Tuesday. “It is very important at this point, to be very careful on what to do with the Taliban.”

“We will remain vigilant in monitoring threats ourselves and will maintain robust counterterrorism capabilities in the region to neutralize those threats if necessary — as we demonstrated in the past few days by striking ISIS facilitators and even threats in Afghanistan, and as we do in places around the world where we do not have military forces on the ground,” Blinken said.

Taliban and al-Qaeda
Afghanistan is almost entirely controlled by the Taliban now, and the Islamist militant group “has never cut off their ties with international terrorist groups” such as al-Qaeda, Noor said, pointing to a video that showed a close ally of Osama bin Laden back in Afghanistan.

Bin Laden founded al-Qaeda, the terrorist organization that was behind the Sept. 11 attacks in 2001 when nearly 3,000 people were killed after hijacked airplanes slammed into the World Trade Center and the Pentagon.