"We won't have peace until we have more leverage for those talks," Evelyn Farkas told Clarissa Ward
on CNN's "Amanpour
"So frankly speaking, I feel like the talks are a charade," she said.
"We are not working hard enough -- we haven't come up with enough leverage to actually get Russia and Syria incentivized to make a compromise."
Farkas stepped down in November as a deputy assistant secretary of defense, the top American military official on Russia policy.
World powers are waiting to reconvene for peace talks in Geneva, Switzerland; previous negotiations achieved a tenuous cessation of hostilities, but nothing approaching a broad agreement to end the war.
Speaking last week in Vienna, Austria, U.S. Secretary of State John Kerry said that "no one can be remotely satisfied with the situation in Syria" but that Russia has "worked closely with the United States" on maintaining the cessation of hostilities.
"Russia has made it very clear to us at least," Kerry said, "that President (Bashar Al-Assad) has made a series of commitments to them, that he's prepared to engage seriously in Geneva."
But Farkas told Ward, "The Russians, they are using the same playbook that Milosevic used in Bosnia," referring to ex-Yugoslav President Slobodan Milosevic's actions during the Balkan wars of the 1990s -- gaining territory militarily to use later as negotiating leverage.
"They did that in Bosnia; Milosevic did that. The Russians are doing it with the Syrians now in Syria."
Speaking in Vienna alongside Kerry, Russian Foreign Minister Sergey Lavrov committed his country to working toward a "full cease-fire nationwide."
However, Farkas said, "Don't let the Russians fool you and the world with their rhetoric about terrorism. They're not fighting terrorism -- they're defending Assad."
She was equally blunt to critics who say the Syrian War has become too intractable for the United States to play a constructive role. "Nothing is ever impossible," Farkas said.
During the Bosnian conflict, she said, some observed that " 'well, those people have been fighting each other for centuries; you know, we can't change that.' Well, yes we can, and we did."
"The fighting is going to go on unfortunately. And that's why, I think -- I hate to say call for more fighting -- but we need to put more military pressure on the Russians and the Syrians.
"Without that, they're not going to compromise unless we come up with something clever, like more sanctions that we implement, not just with our European allies but also with our Middle Eastern friends and partners."