Qatari officials did not respond to requests for comment about the Taliban presence.

“With the Taliban, the Qataris have a hot potato,” said an Afghan journalist working here, who spoke on the condition of anonymity for fear of being expelled. “How do you handle hosting suicide bombers? They can’t acknowledge them until that sort of activity stops.”

The Taliban representatives here are not lightweights. The most prominent among them is Tayeb Agha, the chief of staff to the Taliban’s leader, Mullah Muhammad Omar. Others include Sher Mohammad Abbas Stanikzai, the former Taliban health minister, and Qari din Mohammed Hanafi, their former minister of planning. The delegation includes veteran diplomats like Mualavi Shahabadin Delawar, the former Taliban ambassador to Saudi Arabia; Sohail Shaheen, a former ambassador to Pakistan; and Hafiz Aziz Rahman, the representative to the United Nations for the Taliban government when it ruled Afghanistan.

Just why the effort to open a Taliban office has faltered is a matter of dispute. The Americans say the Taliban have simply decided to continue fighting, worried by pressure from their own hard-liners and concerned that entering peace talks would sap their will on the battlefield. “No one wants to be the last one to die before peace talks start,” as one diplomat put it.

The Taliban say the Americans reneged on their confidence-building pledge to free the Guantánamo five, which would have been politically difficult forPresident Obama, given bipartisan opposition in Congress to such releases. Instead, the Americans insisted that talks would have to include the Afghan government first. The Taliban has rejected that condition, deriding the government of President Hamid Karzai as a puppet regime and saying it would talk to the Afghan government only after reaching a settlement with the Americans.

Still, neither Western diplomats nor the Taliban have given up on the idea of talks in Qatar. “There are Taliban all over the place talking about peace, but the U.S. government’s view is that the most promising is the Doha track,” one diplomat said.

Wahid Muzhda, a former official in the Taliban’s Foreign Ministry who now lives in Kabul but maintains contacts with the insurgents, said that “some of the Taliban still believe it’s worth having the office there, but its prospects do look dim.”

Both Taliban and American officials publicly agree on one thing: that they are no longer talking to each another, officially or unofficially.