Last year, persistent calls from Europe led NATO into military action in Libya. Those passionate voices have been silent on Syria.

France and Germany are expected to push Russian President Vladimir Putin to agree to tougher measures against Syria when he visits Paris and Berlin on Friday. But with Europe bedeviled by economic crisis and political upheavals, few here expect its leaders to galvanize world opinion for a major intervention.

Instead, European leaders who once pushed a cautious Obama administration into action are far more likely now to toe the line on Syria as their energy is expended on protecting their fragile currency. That leaves the fragmented Syrian opposition with no Western partner willing to commit to a significant role in helping to oust President Bashar al-Assad, even as he escalates his iron-fisted tactics to suppress dissent. The United Nations has blamed his government in the massacre last week of more than 100 civilians in the village of Houla.

As the death toll in the 14-month-old uprising rises to more than 10,000, according to U.N. estimates, Syrian opposition leaders have decried the U.S. and European reluctance to come to their aid. But officials on both sides of the Atlantic say Syria is far more complex than Libya was, and many question whether military intervention would actually help.

Asked Thursday whether he could envision a situation in which the United States would take military action in Syria without U.N. authorization, Defense Secretary Leon E. Panetta said, “No, I cannot envision that because, look, as secretary of defense, my greatest responsibility is to make sure when we deploy our men and women in uniform and put them at risk, we not only know what the mission is, but we have the kind of support we need to accomplish that mission.”

Speaking in Denmark, a key member of last year’s campaign against Libya’s Moammar Gaddafi, Secretary of State Hillary Rodham Clinton acknowledged Thursday that on Syria, “we’re nowhere near putting together any type of coalition other than to alleviate the suffering.”

Clinton said the United States has been cautious for many reasons. Unlike in Libya, there is no unified opposition against Assad, and those fighting his rule don’t control significant territory. The Syrian military is much stronger than Gaddafi’s. The Arab League has not called for military intervention, as it did in Libya. And the prospect of a sectarian civil war that could engulf the region is also worrying.

European leaders have echoed those concerns. They are also keenly aware that they can do little without the aid of superior U.S. capabilities to destroy antiaircraft systems, refuel in mid-flight and carry out complex reconnaissance and targeting.

In March 2011, French President Nicolas Sarkozy convened late-night meetings to push an on-the-fence United States into a major bombing campaign as Libyan government forces surrounded the rebellious city of Benghazi.

More than a year later, Gaddafi is gone, killed near his home town. But Sarkozy is out, too, and so is Italian Prime Minister Silvio Berlusconi, Sarkozy’s ally in the Libyan intervention, both victims of politics.

“The atmosphere in Europe has changed fundamentally. Yes, we were in an economic crisis in 2011, when Libya happened, but there was still a sense it was a manageable crisis. Europe had confidence that it doesn’t have today,” said Tomas Valasek, director of foreign policy and defense at the Center for European Reform in London.

In France, voters booted out the hyperactive Sarkozy last month, opting for Francois Hollande. He appears unlikely to push for intervention in the way his predecessor did in Libya, although France and others in Europe imposed bans on oil imports from Syria late last year.

In Britain, where Prime Minister David Cameron was the other major partner in persuading the United States to take part in the Libya action, the government is confronting a slow-boiling scandal over media ethics. Cameron’s austerity-driven efforts to overhaul his country’s economy also have run aground.

And Italian Prime Minister Mario Monti is an unelected technocrat who replaced Berlusconi late last year. Berlusconi gave over Italian air bases for the bombing campaign against Libya. But Monti lacks the political mandate to push ahead on military intervention in Syria.

“There is absolutely no champion for Syria,” said Shashank Joshi, a research fellow at the Royal United Services Institute in London. “March last year was a fairly propitious moment for Sarkozy and Cameron to lead the drive on Libya and take the case to the White House. They just didn’t have the same domestic distractions.”

Germany, which has a long history of caution about military intervention, declined to take part in the Libya action. But Germany stands the best chance of swaying Putin toward a tougher line against Syria.

German Chancellor Angela Merkel said Thursday that she would talk about Syria during Putin’s visit, which had been scheduled to focus on economics.

“A disaster is taking place in Syria, and we will do everything we can to alleviate the suffering of the people,” Merkel told reporters in Stralsund, Germany.

“There’s growing demand to do something,” said Stefan Kornelius, foreign editor of the German daily Sueddeutsche Zeitung. “But nobody knows what that something would be.”

Staff writer William Wan, traveling with Panetta, contributed to this report.