Those who oppose greater U.S. involvement in Syria were no doubt relieved at the announcement that Moscow and Washington want to convene an international conference to end the country’s civil war.

They shouldn’t be.

Secretary of State John Kerry’s announcement contains no hint of a diplomatic breakthrough. Indeed, diplomacy stands no chance unless President Obama first does what he has long avoided: takes the lead in helping the Syrian opposition break the military stalemate on the ground.

Take a look at what actually happened last week in Moscow. Kerry and his Russian counterpart, Foreign Minister Sergei Lavrov, said they would bring representatives of the Syrian government and opposition together to determine how to implement a plan for a political transition, based on a June 2012 agreement reached by the five permanent members of the U.N. Security Council in Geneva, Switzerland.

But this accord has gone nowhere over the last year for compelling reasons. Neither Bashar al-Assad nor Moscow nor, for the most part, the opposition has shown any interest in it. And even when opposition leaders were willing to talk, Assad responded with atrocities, and Moscow did zip.

Did anything change last week in Moscow? Not much. True, Kerry publicly dropped the U.S. demand that “Assad must go,” which had been regarded as a precondition for talks. That gesture, however, won’t make the difference: The reason Assad has spurned the Geneva road map goes much deeper than that.

The Geneva document calls for a transitional government to be formed by mutual consent in negotiations between the government and opposition. That transitional government would exercise full executive power until a new government is elected.

Of course, opposition negotiators would never agree to a transitional government that includes Assad or his inner circle. But no one can imagine Assad voluntarily giving up power.

“According to the terms of the Geneva communiqué, Assad has to agree to go, but he’s not going to choose to go,” said the Syrian American activist Louay Sakka, cofounder of the Syrian Support Group. “Assad wants to hold on.”

Fred Hof, a former State Department adviser who helped negotiate the Geneva document, says Assad realized its terms amounted to “a death sentence” for his family’s rule in Syria. Russia realized this, too, and consequently backed Assad’s rejection of the initiative, even trying to renegotiate key passages.

Early this year, a top Syrian opposition leader, Moaz al-Khatib, offered to talk with government figures less tainted than Assad’s inner circle, and suggested that Moscow help organize such a meeting. French President Francois Hollande asked Russian President Vladimir Putin to facilitate, and thought he’d received a positive answer. But Putin did nothing. Criticized by other opposition leaders for his offer, Khatib has now given up his leadership role.

There was little sign in Moscow last week that Putin had grown more enthusiastic about jettisoning Assad. Many journalists focused on Foreign Minister Lavrov’s statement that Russia is “not interested in the fate of certain persons, [but] in the fate of Syria itself.”

However, Lavrov has said similar things before. He probably means that, should Assad’s inner circle choose to oust him, Russia wouldn’t oppose it. But that is highly unlikely, since members of the inner circle are so tightly connected to Assad that if he goes, they know they will be next.

More telling, when it comes to Russian thinking, is the fact that Putin kept Kerry waiting for three hours, and that intelligence reports surfaced just after Kerry left that Russia was completing a sale of sophisticated surface-to-air missiles to Syria. Such missiles will give Assad far greater protection against air attack, including future Israeli attempts to prevent the transfer of missiles to the radical Lebanese movement Hezbollah.

No hint here that Putin is ready to abandon Assad.

Moreover, all signs indicate that Assad still believes he can outlast the opposition, especially since Obama is so clearly unwilling to help it in a meaningful way.

Hof believes Assad’s suspected limited use of chemical weapons was meant to signal to any waverers in his security circle that Obama would not honor his declared “red line.” “He wanted to reassure his supporters that the West would not intervene,” the former diplomat told me.

Hof also believes there will be no diplomatic breakthrough unless the military balance shifts: Only if Russia believes its proxy could lose might Putin decide the time has come to pressure Assad. I agree.

Changing the balance would not require U.S. boots on the ground, nor should it involve U.S. planes and missiles. But it would require additional military aid from the United States and its allies and a far greater U.S. role — led from the top — in ensuring that aid is channeled solely through the opposition’s new Supreme Military Council.

Given that U.S. commitment, it would be possible to prevent additional weapons from flowing to jihadis. The fact is that the jihadis already have far more access to heavy weapons than the CIA-vetted opposition commanders we claim to support.

Unless the military balance shifts, talk of diplomacy is little more than an excuse to ignore atrocities and red lines. The choice is not between diplomacy and greater U.S. involvement. Without the latter, the former will fail.