Washington has instead continued to pursue a strategy of “leading from behind.” It does so in part out of a belief that a more gung-ho approach may in fact deflect from efforts by members of the opposition’ and paint them as the West’s stooges, as the government has claimed. But as the killings mount, this policy is merely heightening suspicions that America is not serious about supporting the protests and preparing for a post-Assad Syria.

This strategy is not working. America and Europe must push Syria’s neighbors to support punitive measures against Assad and apply diplomatic pressure on Russia and China.

Russia’s warning after the United Nations vote that Mr. Assad should carry out reforms and restore peace or face “some kinds of decisions” from Russia presents an opening. Arab states were crucial in pressuring Russia and China when it came to achieving effective United Nations action in Libya and must do the same now.

Washington should also encourage Turkey to play a more forceful role; the increasingly exasperated Turkish prime minister, Recep Tayyip Erdogan, now seems more likely to do that. Specifically, Turkey should reduce trade with Syria and place targeted sanctions on the government.

The United States should also recognize the Syrian National Council as the legitimate opposition leadership of the Syrian people and encourage key Arab, regional and European powers to do the same. The decision by European foreign ministers on Monday to welcome the council as “a positive step forward” is a useful riposte to Syrian threats against those who formally recognize the group, but it does not go far enough.

The Syrian National Council’s 230-member body represents a broad and inclusive, if imperfect, cross-section of the Syrian opposition — including secularists, Islamists and, critically, the young generation of street protesters risking their lives. International recognition would make it more effective and send a strong signal of support to the opposition.

In addition, the United States should push the Syrian National Council to be as inclusive as possible, particularly in attracting members of the Alawite and Christian communities.