Speaking in London today, James Dobbins said an earlier move might have prevented a Taliban resurgence and would have lessened its force.
"I think we made several mistakes back in 2002," he said about the era just after the successful U.S.-led invasion toppled the Taliban in response to the 9/11 attacks on the United States, which were planned by al-Qaida leaders based inside Afghanistan. "I think it was probably a mistake to delay a serious attempt at reconciliation until 2011."
The envoy also said the 2003 invasion of Iraq shifted US attention away from Afghanistan at a crucial time, giving the Taliban time to regroup and raises funds.
"The decision to move onto Iraq ultimately made it more difficult to turn attention back to Afghanistan once the situation there deteriorated," he said. "So by 2005, 2006 it was clear that much more needed to be done in Afghanistan and we simply didn't have the resources to do so."
Hopes for peace talks have diminished with the Taliban refusing to talk directly to Afghan President Hamid Karzai, his government or its representatives. Attempts to open talks between Afghanistan and the Taliban in June ended in failure.