President Vladimir Putin’s intransigence over Ukraine risks turning him into a global pariah should the blame for downing a Malaysian Airlines jet with 298 passengers and crew members aboard fall on pro-Russia rebels in eastern Ukraine.

The crash of the Boeing Co. 777 followed by less than 24 hours the imposition of new sanctions against Russia that targeted major energy companies and banks. While the rebels denied accusations by the Ukraine government that they shot down the flight, the U.S. said this week that the separatists are being supplied with more heavy weaponry from Russia.

“If there is solid evidence that it is the militants who did it and the weapon originated in Russia, there will be really strong pressure on Putin to really contribute to de-escalation,” Masha Lipman, an analyst at the Carnegie Moscow Center, said by phone. “This should change the way all nations, and not just the West, regard this conflict in Ukraine, and Russia’s role in it.”

Putin, whose popularity has soared to near-record levels since March, when he annexed Ukraine’s Crimea Peninsula, denies accusations of supplying arms and volunteers and says he is trying to broker a peace settlement. The Russian leader Thursday expressed condolences over the tragedy, as did Prime Minister Dmitry Medvedev.

Until now, Putin has been able to stand firm against economic sanctions and Western finger-wagging. The tragedy, should investigators find it was caused by Russian-armed and poorly trained Ukrainian rebels, raises the stakes.

Locked in a Cold War-style standoff with the U.S. and Europe over the future of Ukraine, Putin may have to rein in the rebels if he realizes he has unleashed an “uncontrollable force,” according to Angela Stent, director of the Center for Eurasian, Russian and East European Studies at the Georgetown University School of Foreign Service in Washington.

Putin told his economic Cabinet on Thursday that the Ukraine government was responsible for the tragedy because if there were no war it wouldn’t have happened, according to an official transcript of the meeting. Putin said he ordered all his agencies, military and civil, to do everything to “investigate this crime.”

“Such things are absolutely unacceptable,” he said, according to the transcript.

A Kremlin spokesman, Dmitry Peskov, declined to comment on an Interfax report, citing an unidentified Russian aviation official, that the Malaysian Airlines flight bound for Kuala Lumpur from Amsterdam may have been downed by a Ukrainian rocket attempting to shoot down Putin’s plane. Putin returned from a trip to Latin America on Thursday.

There were 154 Dutch passengers on the plane, Huib Gorter, the Malaysian Airline System Bhd. executive in charge of Europe, told a news conference at Amsterdam’s Schiphol Airport on Friday. French Foreign Minister Laurent Fabius said Flight MK17 may have carried at least four French people. Other travelers came from a range of countries that included Australia, the U.K., Belgium, Canada and the Philippines, Gorter said.

As governments including the U.S., France and the Netherlands gather information on how many of their citizens died, international outrage over the incident should prompt measures to end the fighting, said Ian Bremmer, president of the Eurasia Group in New York.

“Would be a good time for Putin to reassess ‘all-in’ Ukraine strategy. But hard to imagine he’s going to back down,” Bremmer said in comments posted on his Twitter Inc. account.

The downing of the aircraft may push Ukrainian President Petro Poroshenko to escalate his military campaign against the rebels, and possibly spark Russian involvement, said Bremmer. “I do not believe Putin can allow the Ukrainian government to simply remove the separatists,” he said in an interview with Bloomberg Television.

Ukrainian separatists in the eastern part of the country aren’t entirely under Russian control, said Sam Charap, a senior fellow for Russian and Eurasia at the International Institute for Strategic Studies, a Washington policy group. The rebels are “like the Russian Taliban, the people in Luhansk and Donetsk, they’re a proxy force being used to terrorize a neighbor.”

The crash could well cause Russia to pull back tactically, he said.

“I don’t think they’ll completely give up, but maybe rein in some of the crazies that they’ve let loose, and enforce greater discipline,” Charap said in a telephone interview.

In 1983, when Korean Air Lines Flight 007 was shot down by a Soviet warplane over the Sea of Japan, the strike was denounced by then U.S. President Ronald Reagan as a “massacre” and a “terrorist attack.” The Soviets said they suspected it was a U.S. spy plane.

The downing widened the rift with the U.S., with the former Soviet Union forced to veto a United Nations resolution condemning its actions. In the aftermath of the attack, the U.S. was able to rally support among allies for the deployment of Pershing missiles in West Germany.

The European Union and the U.S. may ultimately be moved to take harsher action as a result of the crash, Stent said. “We could get much tougher sanctions out of this than the ones announced yesterday if Russia doesn’t come back to the table,” Stent said.

In its latest measures the U.S. targeted some of the country’s largest corporations, including oil producer OAO Rosneft, gas company OAO Novatek and lender OAO Gazprombank, by effectively cutting their access to American capital markets.

Putin told U.S. President Barack Obama in a phone call Thursday he is “seriously disappointed” at the sanctions, which won’t help to end the conflict in Ukraine, according to a Kremlin statement.

The plane, which was downed at an altitude of 33,000 feet (10,000 meters), was most likely shot with a Buk anti-aircraft system, which requires a specially trained unit, said Mikhail Khodarenok, editor-in-chief of Defense Industrial Courier.

“I have doubts that (the) Ukrainian Army has people to use such weapons and that militants have such people,” he said by phone.

A White House official said that a Ukrainian military transport plane shot down over eastern Ukraine on July 14 with eight crew members on board was flying at an altitude of 21,000 feet and could only have been shot down by very sophisticated weapons systems.

The official said that the flow of heavy weapons from Russia and support for Russian separatists has increased over the past month. The training and tactics of rebels in eastern Ukraine has also grown more sophisticated, the official said.

Sergei Markov, a political analyst who consults with Putin’s staff and often represents the view inside the Kremlin, said Putin won’t be pressured into renouncing all support for the rebels in eastern Ukraine.

“Putin will continue acting in the same way,” said Markov. “What else can he do? Send in troops? Stop all help for the anti-fascist rebels? We all know that a band of armed criminals controls Kiev.”

The aircraft shooting highlights the conflict in Ukraine and Russia’s role in it, according to Carnegie’s Lipman. “We are dealing with a ragtag army who have been armed with high-precision weapons and are shooting at anything that moves,” she said.