KABUL, Afghanistan — A giant H has been painted on the broad boulevard in front of the American Embassy in Kabul, creating a new helipad that recently, embassy officials say, has been used only by Zalmay Khalilzad, the special United States diplomat who has been talking with the Taliban.

President Ashraf Ghani of Afghanistan usually uses the roads, moving in armored convoys that snarl traffic in the gridlock-weary capital.

The pecking order is clear. As American policy in Afghanistan seems bent more than ever on making a deal with Taliban insurgents to withdraw American troops from the country after nearly two decades of war, Mr. Khalilzad’s diplomacy is taking priority.

The talks between Mr. Khalilzad and the Taliban, while full of caveats, have raised some parallels to Henry A. Kissinger’s talks with North Vietnamese leaders, which presaged the American pullout from South Vietnam in 1973 and the collapse of South Vietnam two years later.