KABUL, Afghanistan — All around Kabul, the broken glass was being swept and the dead were still being buried on Thursday. They were the most visible signs of the toll taken by the huge truck bombing in the capital the day before, but another casualty of the violence may yet come into view: a new attempt to move toward peace negotiations with the Taliban.

Over the past several weeks, the Afghan government and the foreign missions here have been preparing for a conference on Tuesday 6 in which senior representatives from nearly two dozen countries were to gather in Kabul to discuss the war.

The plan was that President Ashraf Ghani would use the conference as a venue to try to build international support as he emphasized that his government was recommitted to the idea that negotiations were needed. Officials characterized it as an Afghan attempt to bring all the regional and political players together to try to take control of a process that has repeatedly been derailed by a lack of cooperation from neighboring powers and by Taliban military gains.

But the bombing, which the government says was committed by the Haqqani wing of the Taliban, has cast a shadow over the effort in several ways — a demonstration of how fragile even the earliest steps of peacemaking can be in the middle of a war.