The main reason for making a deal with Mr. Assad right now — even one where he is initially offered more carrots than sticks — is precisely that a Western-led process that steadily undermines his ability and desire to use violence would stabilize a quickly deteriorating regional situation, gradually opening up Syria’s political system and reducing repression over time…

In exchange, a robust and competent contingent of Arab and United Nations monitors should promptly fan out across the country in order to verify the army’s pullback of heavy weaponry and the steady release of political prisoners. They would provide a permanent presence, and citizens could approach them to register complaints about violence committed by any side.

A national reconciliation conference outside of Syria should then be convened under Arab League and United Nations auspices. This would lay the groundwork for writing a new constitution and holding multiparty, supervised parliamentary elections later this year — as Mr. Assad himself recently proposed — and presidential elections in 2013. The reconciliation conference should also begin an investigation into the violence of the past year.

Three incentives could make the deal extremely difficult for Mr. Assad to reject.