Last week, U.S. President Obama urged Mid-East leaders to play an active role in stopping the bloodshed in Syria saying, "We continue to see unacceptable levels of violence inside that country." His comments echoed those of UN Secretary-General Ban Ki-moon who earlier noted, "the situation in Syria has reached an unacceptable point," while calling upon the Security Council to act with "seriousness and gravity and in a coherent manner."

Indeed, the death toll now stands at close to 6,000 persons murdered in uprisings against the Assad regime since protests began last March, including indiscriminate sniper fire, even at funerals; the wonton killing and torture of children, detainees, and hospital residents -- in short, the slaughter of innocents.

Yet there is reason to fear that we have not yet witnessed the worst -- as events of the last week clearly demonstrate. Violence has started to erupt in the Syrian capital, Damascus, which has thus far been spared. President Assad last week broke his public silence, calling for protesters -- whom he labeled as "terrorists" -- to be "hit with an iron fist."

Arab League observer Anwar Malek defected from the League's observation mission, telling reporters: "What I saw was a humanitarian disaster. The regime isn't committing one war crime but a series of crimes against its people," and that the observer mission was facilitating rather than preventing violence.

Indeed, as U.S. Ambassador to the United Nations Susan Rice put it, "Since the Arab League monitoring mission has been on the ground, in fact an estimated 400 additional people have been killed, an average of 40 a day, a rate much higher than was the case even before their deployment."

While the Arab League has suspended Syria and adopted unprecedented sanctions against the regime -- including economic and financial sanctions, travel bans, and asset freezes -- the killing continues. The Syrian Government's response continues to be more mayhem, more murder, more cruelty, more arrests, and more disappearances in what has been the most heroic and impressive of protests in the Arab world. Indeed, in no Arab country -- not Tunisia, Egypt, or Libya -- has such restrained civilian protest encountered such violent and sustained state repression, as cruel as it has been massive.

To address the situation, the Arab League is considering extending its mission, EU Ministers are expected to discuss European sanctions against Syria next Monday, and a meeting of Arab foreign Ministers is set for Tuesday. But, while sanctions are helpful, what is needed now is urgent action by the UN Security Council to implement the Responsibility to Protect (R2P) doctrine with respect to Syria.

It is as astonishing and it is shameful that the UN Security Council has yet to adopt a resolution of condemnation, let alone invoke R2P. Regrettably, Syrian allies Russia and China are using their presence on the Security Council to reject any meaningful action.

At the U.N. World Summit in 2005, more than 150 heads of state and governments unanimously adopted a declaration on the Responsibility to Protect, authorizing international collective action "to protect [a state's] population from genocide, war crimes, ethnic cleansing, and crimes against humanity" if that state is unable or unwilling to protect its citizens, or worse, as in the case of Syria, if that state is the author of such criminality.

The doctrine was first referenced in the case of Kenya's post-election violence in 2007-2008. Earlier this year, the doctrine was explicitly invoked by the UN Security Council after the bloodletting in Libya.

Since the mass protests in Syria began, those seeking freedom and democracy have looked for international support and solidarity in their struggle against the murderous regime. But, inaction and indecision from the rest of the world have allowed the situation to escalate and more than a ten-fold increase in civilian deaths -- and the attending torture and cruelty -- has occurred as a result. We cannot afford to delay any longer before implanting R2P.

In particular, the international community should ensure the deployment of a international protection force lead by the Arab League; the provision of badly-needed humanitarian assistance and relief; the withdrawal of Syrian tanks and troops to barracks; the implementation of no-fly and no-drive zones; and support for the Syrian National Council, the nascent Syrian representative body.

Other possible measures would include: implementing worldwide travel bans and asset seizures, expanded economic and financial sanctions, an arms embargo -- with Russian compliance -- and, perhaps most important, the initiation of international criminal investigations for war crimes and crimes against humanity, while putting Syrian leaders on notice that they will be held responsible for their crimes.

As UN Secretary General Ban Ki-moon once put it, "loss of time means more loss of lives." The Security Council must act -- and China and Russia must be called to account for their obstructionism. It is our collective responsibility to ensure R2P is not empty rhetoric, but an effective instrument for preventing mass atrocity, protecting people, and securing human rights.

Tragically, we have not yet done what still needs to be done despite our knowing the cruel and desperate reality of the situation on the ground in Syria for close to a year now. Indeed, the Economist ran a cover story entitled "Savagery in Syria" last April. No one can say we did not know. Yet, after all this brutality, we still do not have a protective UN Security Council resolution. If the R2P is to mean anything, it means acting here -- and acting now.