ABC News' Kirit Radia (@kiritradia_abc) reports: As the Syrian government’s brutal crackdown on protesters continues, so do calls for the international community, and the United States, to do more to end the bloodshed. But what can the U.S. realistically do to convince President Bashar al-Assad, once considered a reformer, to pull back his troops and set the country on the path towards democratic reform? And why has Washington been reluctant to take more drastic action despite reports of a slaughter? The Obama administration has taken some steps already – slapping sanctions on the regime and its interests for human rights abuses and upping the rhetoric on President Assad – but has balked at pleas to pull its ambassador in Damascus or intervene militarily. So what can and should be done? This week I put the question to Andrew Tabler, a Syria expert at the Washington Institute for Near East Policy who spent eight years living and reporting there. His new book “In the Lion's Den: An Eyewitness Account of Washington's Battle with Syria” comes out in September. His solution involves beefing up sanctions, in particular on Syria’s energy sector, and working with the opposition inside Syria and abroad in order to ratchet up the pressure on Assad. A military option, he says is unlikely to garner much support internationally or to succeed in changing Assad’s behavior. Tabler says the recent experience in Libya has soured global opinion on the use of military intervention to defend civilians against a regime’s violence. The NATO operation in Libya is in its fourth month and Libyan leader Moammar Gadhafi maintains a grip on power despite daily bombing runs on his defenses. Tabler says a military operation in Syria could face the same problems. “It is unclear exactly what could we do militarily that would actually knock out the regime. Would it require just missile strikes? I think it would require more than that. So what would it be? Would it be an invasion? Are we prepared to invade Syria?” he asked skeptically. In the case of Libya, NATO intervened with the backing of the Arab League and the United Nations Security Council, which authorized military actions to defend civilians. So far, no such international support exists to provide cover and legitimacy for similar actions in Syria. Yet despite the failure to move any condemnation through the U.N. Security Council, where perennial roadblocks Russia and China have scuttled efforts to pressure Syria, Tabler says global condemnation has historically affected the regime’s actions and suggests international opposition may disappear if the crackdown continues. “As the massacres go on and the Syrian regime doesn’t come up with a good plan to deal with them, Russian, Chinese, and Indian opposition to pressuring Syria could melt away,” he says. Is there anything Washington could do on its own to budge Assad? Tabler says the regime is only concerned with its survival. “As long as you threaten his survival, if you make it as hard as him as possible, and you have to be ruthless at that, as is he is with us, then I think you'll start seeing him move,” he says. And what does "ruthless" mean? “Ruthless would be not just saying, for example, we're supporting the Syrian opposition conference, we said it was a good first step. That’s fine, that doesn’t mean we let up on the pressure on the energy sector for example or diplomatically. We play both at the same time. You have to pressure and engage fruitfully at the same time,” Tabler says. To that end he advocates expanding sanctions on Syria to include measures against the lucrative petroleum industry which he says is the source of up to a third of the government’s revenue. “There's more they can be doing on energy and they need to accelerate that. We just need to follow through on it. We shouldn’t hesitate,” he said. Last month senior administration officials, speaking on the condition they not be quoted by name, revealed the Obama administration is exploring sanctions on Syria’s petroleum sector. Other officials, however, say it will take some time to put those measures together. “If you really want to pressure the Assad regime, targeting energy makes sense because it deprives them of a source of revenue,” Tabler argues, adding that such financial pressure could create internal tensions that could move Assad to make a deal. Some key lawmakers have urged President Obama to withdraw Ambassador Ford from Damascus, especially after he attended a regime-sponsored trip to towns near the border with Turkey. Ford had already made enemies on Capitol Hill who blocked his nomination as ambassador until President Obama circumvented the block by giving him a recess appointment. They saw his appointment as rewarding Syria for bad behavior in the region. Last month’s trip was only fuel for the fire. Tabler, however, says Ford has done more good than harm in his role. “Ford's duties are not just talking with the regime, it's also about talking with the opposition and I know he's been involved in that, he's been involved in getting people freed. The question is not just about Ford, it's about our policy,” he said. Others have urged President Obama to finally call on Assad to step down, much as he has done with Libya’s Gadhafi. In his May 19 speech on the region, Obama called on Assad to reform or get out of the way, but stopped short of calling for his ouster. Tabler points out that move would invite more questions about what the administration will do to make it happen. “The reason why they don’t do that is because once they’ve said it then they’re committed to it,” he says. He points out that suggestions that the U.S. restrict the Syrian ambassador’s movements to just 25 miles around Washington would only invite reciprocal restrictions on Ambassador Ford. Tabler also recommends building up the Syrian opposition, something the U.S. is already supporting both inside and outside the country. Another suggestion involved an investment ban which, while the U.S. doesn’t have much investment in Syria, could have a trickle on effect particularly in the energy sector. While Tabler makes a good case why tougher sanctions, especially on the oil sector, could affect change in Syria, it’s worth noting such measures have failed to change the behavior of other regimes. Repeated rounds of sanctions on Iran’s leadership and their business interests have yet to convince Tehran to cease its nuclear activities. If sanctions are to work in Syria, the oil sector sanctions will have to be strong enough and with enough international support to sufficiently squeeze Assad to reform. Otherwise Washington will have to continue grasping for leverage in Damascus.