The only known genuine negotiating channel to those leaders was developed by US and German diplomats, who spent roughly two years trying to open peace talks in Qatar. The diplomats repeatedly found themselves incurring the wrath of Karzai, who saw the effort as an attempt to circumvent him.
Then, when a US diplomatic push led to the opening of a Taliban office in Qatar, Karzai lashed out publicly at the US. Afghan officials said that to them, the office looked far too much like the embassy of a government-in-exile.
Within days, the Qatar initiative stalled, and Karzai was fuming at what he saw as a plot by the US to cut its own deal with Pakistan and the Taliban without him.
In the wake of the failure in Qatar, Afghan officials redoubled their efforts to open their own channel to Omar, and by late autumn, Karzai apparently believed those efforts were succeeding.
Some senior Afghan officials say they did not share his confidence, and their doubts were shared by US officials in Kabul and Washington.
Both Karzai and US officials hear the clock ticking. US forces are turning over their combat role to Afghan forces and preparing to leave Afghanistan this year, and the campaigning for the Afghan national election in April has begun.
An orderly transition of power in an Afghanistan that can contain the insurgency on its own would represent the culmination of everything that the US has tried to achieve in the country.
If the peace overture to the Taliban is indeed at an end, as officials believe, it is unclear what Karzai will do next.
He could return to a softer stance on the security agreement and less hostility toward the US, or he could justify his refusal to sign the agreement by blaming the US for failing to secure a genuine negotiation with the insurgents.
Karzai has insisted that he will not sign the agreement unless the US help bring the Taliban to the table for peace talks.
Some diplomats worry that making such a demand allows the Taliban to dictate the terms of the US’ long-term presence in Afghanistan.
Others question Karzai’s logic: Why would the insurgency agree to talks if doing so would ensure the presence of the foreign troops they are determined to expel?