The United Nations special envoy for Syria said Wednesday that he had invited a range of Syrians to participate in what he described as preparatory, separate discussions on how to restart peace talks after more than four years of war.

In a briefing to the United Nations Security Council, the special envoy, Staffan de Mistura, said such discussions were “aimed at stress-testing any willingness, if there is any, of narrowing gaps” between President Bashar al-Assad’s government and its opponents.

Mr. de Mistura, who is the third United Nations envoy to seek negotiations to resolve the conflict, which began in March 2011, was vague about the timing, participants and venue of such discussions.

But Secretary General Ban Ki-moon, who also appeared before the Security Council on Wednesday, later told reporters outside the chambers that the proposal was aimed at beginning a “step-by-step process to operationalize the Geneva Communiqué,” the 2012 document that became the starting point for Syria peace talks.