By Mark Landler

New York Times

WASHINGTON >> With the humanitarian and refugee crisis in Syria spiraling to new depths, the Democratic and Republican vice-presidential candidates, in their debate Tuesday, called for a more forceful U.S. response to the civil war than President Barack Obama has undertaken.

Even as they argued over Donald Trump’s income taxes and Hillary Clinton’s email practices, the candidates, Gov. Mike Pence of Indiana and Sen. Tim Kaine of Virginia, found some common ground on what is perhaps the thorniest geopolitical crisis today.

Both said they favored a proposal to create humanitarian “safe zones” in northern Syria to protect civilians being bombarded by the Syrian government. Neither was precise about what would be needed to create such corridors, though analysts say it would almost certainly require U.S. warplanes to enforce a no-fly zone.

Obama has steadfastly resisted such a step. Until this week, his administration was trying to negotiate a cease-fire with the Russians, who are helping Syrian government forces in their siege of Aleppo.

Pence, Trump’s running mate, said the United States should be prepared not only to enforce a no-fly zone but also to carry out strikes against the forces of the Syrian president, Bashar Assad, to protect civilians.

“If Russia chooses to be involved and continue, I should say, to be involved in this barbaric attack on civilians in Aleppo,” Pence said, “the United States of America should be prepared to use military force to strike military targets of the Assad regime to prevent them from this humanitarian crisis that is taking place in Aleppo.”

Kaine was more circumspect.

“Hillary and I also agree that the establishment of humanitarian zones in northern Syria with the provision of international human aid, consistent with the U.N. Security Council resolution that was passed in February 2014, would be a very, very good idea,” he said.

Kaine did not refer specifically to a no-fly zone, and he conspicuously avoided a question about how to stop the slaughter in Aleppo. Clinton first advocated a partial no-fly zone about a year ago, but she has not fleshed out the proposal during her campaign, and many analysts said it had become unrealistic since Russia intervened in the conflict because of the risk that U.S. planes would exchange fire with Russian planes.

It is at a crucial moment in Syria, with Secretary of State John Kerry giving up after weeks of trying to negotiate a cease-fire with Russia. The suffering in Aleppo has become dire; aid groups estimate that 100,000 children are trapped in the city as Assad’s government bombards it relentlessly in an attempt to crush the rebellion.

Obama’s national security aides are weighing other options, including strikes on Assad’s forces. But the president remains deeply skeptical about greater military involvement. His commanders have been wary of a no-fly zone, saying it would necessitate a huge commitment of troops and aircraft at a time when the United States is deploying planes and soldiers in the military campaign against the Islamic State.

Pence put himself at odds with Trump on this issue. In May, Trump told MSNBC morning-show host Joe Scarborough that he would not take military action against Assad because it would complicate efforts to combat the Islamic State, also known as ISIS or ISIL.

“I would have stayed out of Syria and wouldn’t have fought so much for Assad, against Assad,” Trump said. “Now you have Iran and you have Russia in favor of Assad. We’re supposed to fight the two of them. At the same time, we’re supposed to fight ISIS, who is fighting Assad.”

Pence also used very different words from Trump to characterize President Vladimir Putin of Russia. He described him as “the small and bullying leader of Russia,” who he said was “now dictating terms to the United States to the point where all the United States of America — the greatest nation on Earth — just withdraws from talks about a cease-fire while Vladimir Putin puts a missile defense system in Syria.”

Kaine has had his own differences with Clinton on the use of force. In the Senate, he called for Congress to pass a new authorization for Obama’s military campaign against the Islamic State, something Clinton has said is not necessary.

On Tuesday, he did not seem eager to be drawn out on Syria policy, plunging instead into an extended back-and-forth with Pence over Trump’s relationship with Putin and Clinton’s record as a member of Obama’s national security team.

For Clinton, who has drawn close to Obama during her campaign, Syria has become an awkward issue. While secretary of state, she advocated supplying weapons to the moderate rebels, which he initially rejected. After leaving the administration, she came out in favor of a no-fly zone.

Neither Trump nor Clinton’s opponent in the primaries, Sen. Bernie Sanders of Vermont, has pressured her to explain her Syria policy, and she has seemed content not to discuss it. On Tuesday, however, the debate between the running mates shed at least a bit of light on it.

© 2016 The New York Times Company