Secretary of State Hillary Clinton suggested last Thursday that Bashar al-Assad's days in power seem to be coming to an end. "I wish it would be sooner," she said at a conference in London, "so that more lives would be saved."

Secretary Clinton is right that Assad must go, but the United States would be wise to do more than wish—and quickly. The United Nations has prepared a secret list of top Syrian officials who could soon be charged with crimes against humanity. Before those names become public, the U.S. has a chance to influence Middle East politics in a subtle yet significant way.

Looking to Yemen as a model, the U.S. could offer Assad the same immunity arrangement that former Yemeni President Ali Abdullah Saleh received in exchange for a quiet departure from power. This would save the lives of many Syrians and help break the dangerous political bond between Syria and its patron, Iran.

Saleh's exodus from Sanaa to New York for medical treatment and subsequent return to Yemen so far has had promising results. (He is now reported to be heading to Ethiopia to live there in exile.) His vice president, Abdu Mansour Hadi, was elected—albeit in a plebiscite—in a fair election, and the violence is subsiding. And the U.S. still has the ability to reduce al Qaeda's presence in Yemen.

The analogy between Yemen and Syria is not perfect, but the success in Yemen might encourage the U.S. to propose a similar exit strategy for Assad. The dictator's absence could put an end to the ruthless shelling of Syrian cities without the riskier option of outright military intervention and arming an opposition that is not well understood.

Read more in The Wall Street Journal.