Sen. John McCain criticized U.S. President Barack Obama and Secretary of State Hillary Clinton Sunday for their failure to take more decisive action against Syrian President Bashar al-Assad after 16 months of violent conflict.

My question to the secretary of state and the president of the United States is, how many more have to die before we take action to help these people with other nations? [...] It is shameful, the total lack of leadership that the United States has displayed for the last 14 months.

McCain, Obama's opponent in the 2008 election and the leading Republican on the U.S. Senate Armed Services Committee, made his comments to Bob Schieffer, host of the CBS talk show Face the Nation. McCain has repeatedly demanded stronger action against Assad; in March, he became the first U.S. senator to call for air strikes against the Syrian regime.

According to most estimates, at least 14,000 Syrians have been killed during the popular uprising against Assad, which began in March of last year. The Syrian president has refused to step down, blaming the uprising on terrorist gangs and foreign influences while continuing to brutally suppress the revolt. International intervention has been resisted by Russia and China, which have both wielded veto power over strong resolutions against the Syrian regime by the U.N. Security Council.

Meanwhile, efforts to negotiate a ceasefire under a six-point peace plan, proposed by U.N. special envoy Kofi Annan, have done nothing to stem the bloodshed. In an interview published on Saturday, Annan himself acknowledged its failure.

On Sunday, McCain blasted the Annan plan, arguing that it does not call for Assad to step down. When Schieffer asked what McCain would suggest instead, the senator stopped short of unilateral U.S. military action.

[We work] along with other countries, and we lead for a change, responded McCain. Lead. Not lead from behind, but lead from in front. Over there, they are waiting for American leadership. We have announced that we're now providing them [the rebels] with nonlethal equipment; that doesn't do very well against tanks and artillery.

McCain voiced support for arming rebel forces with anti-tank weaponry. We need to get a sanctuary for the Free Syrian Army, he added. We need to get them supplies, and we need to get them weapons. ... It's not a fair fight.

The senator supported his argument by pointing to successful international interventions in Libya, Bosnia and Kosovo.

For myriad reasons, the Obama administration is hesitant to call for stronger action against Assad. There are concerns that the Syrian rebellion is too fractured and disorganized to take over the country in the event of Assad's departure, and that an empowered resistance movement might endanger minority groups. Furthermore, there is little public pressure on Obama to intervene; the United States population is generally hesitant to engage in another Middle Eastern struggle following more than a decade of wars in Iraq and Afghanistan.