French President Francois Hollande became the first Western leader to call on Syria’s rebel movement to form a provisional government, putting additional pressure on President Obama to back the diplomatic gambit or authorize U.S. military action to protect civilians. (Bertrand Langlois/AP)

Scattershot diplomatic efforts aimed at curbing the worsening violence in Syria grew more complicated Monday, with France urging world recognition of a shadow Syrian government that the United States considers premature.

In making his plea, French President Francois Hollande became the first Western leader to call on Syria’s rebel movement to form a provisional government, putting additional pressure on President Obama to back the diplomatic gambit or authorize U.S. military action to protect civilians.

Hollande said he hoped an internationally recognized alternative Syrian government would speed the fall of President Bashar al-Assad. The United States supports such a unified movement, but on Monday it declined to endorse Hollande’s proposal, which would provide Western backing to a decentralized movement that could include extremist elements.

The latest appeal reflects growing frustration — in France and elsewhere in Europe — with international inaction to stop the bloodshed in Syria. On Monday, at least 148 people were killed in an offensive by Syrian government forces in Damascus and the surrounding area, according to opposition activists. At least 42 people died in an aerial bombardment in the northeast suburb of Zamalka.

Earlier in the day, Syrian rebels shot down a military helicopter over Damascus, according to the rebel Free Syrian Army. Dramatic video footage of the helicopter attack, posted online Monday, showed a smoking aircraft circling horizontally before taking a dramatic vertical dip and plunging to the ground in flames.

The sound of heavy machine-gun fire can be heard on the video, along with chants of “God is great.”

U.S. officials and outside military experts said it is doubtful that rebels used shoulder-fired or surface-to-air missiles to bring down the helicopter. Those weapons are considered game-changers, and it is unclear whether the rebels have been able to get them.

An estimated 20,000 people have been killed in the Syrian conflict, which grew out of pro­democracy protests that began in March 2011. By some measures, the violence has intensified in recent weeks.

On Saturday in the Damascus suburb of Darayya, more than 320 people were killed, many of them shot in the head, in what opposition groups described as the largest massacre of the conflict.

Hollande’s proposal stopped short of an international call to arms but nonetheless recalled former French president Nicolas Sarkozy’s early insistence that the world must act to stop atrocities in Libya under Moammar Gaddafi. Although the White House chafed at the pressure, Sarkozy’s readiness to use warplanes to enforce a zone of protection inside Libya helped drive the Obama administration’s embrace of a no-fly zone.

“France asks the Syrian opposition to form a provisional government — inclusive and representative — that can become the legitimate representative of the new Syria,” Hollande said in a speech to France’s corps of ambassadors.

Many Western nations and Arab countries have called for Assad to leave power, but none has formally recognized the opposition as the country’s legitimate leaders.

Such a government-in-waiting would require Syria’s badly divided political opposition and anti-Assad rebel fighters to unite behind a slate of leaders and a platform. It would probably also mean that extremists would be included among the would-be rulers.

The groups fighting Assad have many motives, and the factions have been slow to coordinate. U.S. officials said they are only now seeing expatriate activists make good on a promise to recruit support inside Syria for a set of unity principles they drafted in early July. The pact would commit rebels and political opposition figures to resist sectarian reprisals and respect human rights.

“They are continuing to confer among themselves,” State Department spokeswoman Victoria Nuland said of the Syrian opposition factions. “What’s most important is that, moving forward, the Syrian opposition outside Syria and the Syrian opposition inside Syria coordinate and collaborate” on the framework and leadership for the country after Assad.

With no appetite in Europe for a major military action similar to last year’s intervention in Libya, attention has focused on political demands that Assad step down, rhetoric that could be strengthened by the formation of an alternative government in exile.

But U.S. officials are concerned that forming a provisional government gets ahead of both the opposition’s internal discussions and international readiness to respond to the conflict. Of greater immediate concern is a plan to deal with refugees flowing into Turkey, Jordan and elsewhere, and consensus on whether protection for refugees might extend to a military-enforced safe zone inside Syria.

France supports the creation of “free zones” for the protection of displaced people inside Syria, such as an idea floated by Turkey of a buffer zone, Hollande said.

France has also convened a U.N. meeting on Syria this week. The meeting coincides with the final day of France’s one-month rotating leadership of the Security Council.

On Monday, Turkey reopened border crossings to a tide of Syrian refugees but warned anew that it cannot house or pay for the influx alone.

Italy, Turkey, the United States and other nations with a large stake in Syria will host a separate strategy session in Rome on Wednesday. Egypt suggested a regional meeting that would include Syria’s patron Iran, but that idea has apparently fizzled.

Iran says it plans talks on a peace plan to end the civil war but has not provided details.

Dehghanpisheh reported from Beirut.