Tuesday’s decision by the United States, Britain, France and at least five other major nations to expel senior Syrian diplomats was a powerful sign of international revulsion at the massacre of more than 100 Syrians in the village of Houla. But it was still short of the tougher diplomatic and economic sanctions needed to put real pressure on President Bashar Assad and his cronies. Russia, in particular, can finally help or continue to be a roadblock to tougher action.

Assad is responsible for killing an estimated 12,000 people during his reign of terror, now in its 14th month. Kofi Annan, the special envoy for the United Nations and the Arab League, was in Damascus on Tuesday trying to keep alive a peace plan under which Assad promised six weeks ago to end the violence. The massacre Friday was just the latest evidence that he never intended to follow through.

According to a U.N. count, the victims included 49 children and 34 women. The government tightly controls access to the country so there is some uncertainty about what happened. A spokesman for the U.N. high commissioner for human rights said fewer than 20 of the Houla victims were killed by artillery — weapons the government possesses and the opposition does not.

Syrian officials blamed “terrorists” for the attacks. We assign far more credibility to villagers who told U.N. monitors that “shabiha,” or government thugs associated with Assad’s Alawite sect, committed at least some of the killings by shooting people — including entire families — at close range.

It is significant that the Security Council acted quickly and unanimously Sunday to condemn the bloodshed and censure the Syrian government for using heavy artillery against civilians, even though it did not actually assign blame. Too often in the past, China and Russia, Syria’s main enabler, delayed council action and twice they vetoed sanctions. Officials from both countries complain that council action could lead to foreign intervention in Syria, as in Libya.

But U.S. Gen. Martin Dempsey, chairman of the Joint Chiefs of Staff, warned Sunday that it is continued atrocities that could make intervention more likely. Any outside intervention risks fueling a wider war. Iran is already meddling and the increasingly sectarian conflict has begun spilling into Lebanon, Turkey, Jordan and Iraq.

Sanctions imposed by the United States, the European Union and others are having an effect. Still, a U.N. arms embargo and the toughest possible comprehensive economic sanctions are long overdue. Russia has the most leverage, but, inexcusably, it still sells arms and coal to Syria and uses its Mediterranean port of Tartus.

We can see no easy solutions to Syria, despite Mitt Romney’s facile criticism of President Barack Obama. In a campaign statement issued Tuesday, Romney called for “more assertive measures to end the Assad regime.”

But he fails to say how he could be more successful at getting Russia to “cease selling arms to the Syrian government” or how arming a fractious opposition could be effective. And there’s no hint of what it means to “end the regime” and whether that would require U.S. troops. Could he possibly be eager for another war? If Romney has good ideas, everyone would like to hear them.

— The New York Times