The Taliban held talks with US officials in Qatar on ending the Afghan conflict last week, the militants confirmed Monday, but said no agreement was reached on "any issue".
Khalilzad was in the Afghan capital after a second round of regional meetings with top government officials to coordinate efforts on ending the 17-year war.
Senior Taliban officials met with a "high-ranking" US delegation in Qatar on November 14, 15 and 16, the militant group said in a WhatsApp message, without mentioning Khalilzad.
The Taliban has a political office in the capital Doha that serves as a de-facto embassy.
"These were preliminary talks and no agreement was reached on any issue," spokesman Zabiullah Mujahid said.
"We want to reassure our Mujahideen and Muslim nation that the representatives of the Islamic Emirate will never agree to anything that does not adhere to Islamic principles."
The second Taliban-US meeting in as many months come as the militants step up attacks on beleaguered Afghan security forces, which are suffering an unprecedented level of casualties.
The death toll among Afghan soldiers and police is nearing 30,000 since the start of 2015, Afghan President Ashraf Ghani revealed this month -- a figure far higher than anything previously acknowledged.
In a recent report, the US Special Inspector General for Afghanistan Reconstruction (SIGAR) cited the NATO mission in Kabul as saying this summer's toll had been worse than ever for Afghan forces.
Khalilzad told reporters on Sunday that he recognised the "complexity" of the conflict, but insisted he wanted to "make as much progress as possible as soon as possible".
His comments underscore an apparent increasing sense of urgency in the White House and among American diplomats for a peace deal to be done quickly.
Washington is facing competition from Moscow, which this month hosted an international gathering on Afghanistan that was attended by the Taliban.
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