UN Secretary-General Ban Ki-moon called Thursday for a weapons blockade on Syria’s warring parties to stop violence from further spilling across borders as it has in Iraq in his most aggressive bid to end the Security Council’s stalemate on dealing with the Syrian civil war.

“I’m here to express my anger and disappointment at the cold calculation that seems to be taking hold: that little can be done except to arm the parties and watch the conflict rage,” Ban said in a speech at the Asia Society in New York. “I urge the Security Council to impose an arms embargo.”

The Security Council, the most powerful body at the United Nations, is deadlocked over efforts to intervene in the Syrian war, with Russia and China blocking multiple attempts at halting atrocities, providing humanitarian aid or ending the violence. Ban’s comments are the strongest he has directed at the council over its impasse, as members take sides in the conflict by providing military aid to the warring parties.

“For the moment, the greatest obstacle to ending the Syria war is the notion that it can be won militarily,” Ban said. “I recognize that an embargo would risk freezing an imbalance in place, given the extent of the government’s weaponry. But the Syrian war cannot be won militarily.”

More than 160,000 people have been killed in the three-year fight between the regime of President Bashar al-Assad and its opponents. The conflict bred the Islamic State in Iraq and Syria, an al-Qaeda offshoot that initiated the Sunni insurgency now threatening the Iraqi government.

The unrest in Iraq portends a possible sectarian war in the region between Shiite and Sunni Muslims, Ban said.

“The Syrian conflict has now spread visibly and devastatingly to Iraq, with flows of arms and fighters across a porous border,” he said. “Syria’s neighbors should enforce a firm prohibition on the use of their land borders and airspace for arms flows and smuggling into Syria.”

He also cautioned against military strikes on the Islamic State jihadist army because they “might have little lasting effect or even be counterproductive if there is no movement toward an inclusive government in Iraq.”

The Syrian Coalition, the U.S.-backed moderate opposition, disagreed with Ban’s call for a weapons blockade, instead demanding “serious weapons and training” for its armed forces to force Assad to accept a negotiated end to his rule, according to a statement on its website.

Vitaly Churkin, Russia’s ambassador to the United Nations, said he is also against an arms embargo, unless Ban can explain how it will be effectively implemented.

“Of course, we have the experience of Libya where there was an arms embargo and weapons were flowing freely to various opposition groups and still floating all over Africa, so we don’t want to go in that direction,” Churkin told reporters today in New York.

“If they explain to us how the arms embargo will be enforced vis-a-vis various armed groups, then we could consider that.”

UN-mediated peace talks collapsed in February with no prospect for resumption as the two warring parties, as well as their backers among other nations, left in dispute over Assad’s future.

“Diplomacy seems to have stopped in its tracks,” Ban said, referring to Lakhdar Brahimi’s exit last month as the chief UN negotiator.

“No one is winning; no one can win.” Ban said. “The sides will have to sit across from each other again at the negotiating table.”

“The only question is how many more people must die before they get there?” he said.