WASHINGTON, D.C.: President Barack Obama proclaimed Syria’s newly reframed opposition as the “legitimate” representative of the nation’s people on Tuesday (Wednesday in Manila), in the most significant US intervention in a brutal civil war.

As Washington cranked up pressure on beleaguered President Bashar al-Assad, the Obama administration also blacklisted the al-Qaeda-linked Al-Nusra Front, which officials feared were seeking to hijack the revolution as a terrorist group.

It was another day of carnage inside Syria, meanwhile, as scores of civilians from Assad’s minority sect were reported killed, in what appeared to be the largest scale revenge attacks against Alawites.

The United States has edged slowly toward recognizing the opposition Syrian National Coalition, and its move follows similar action by France, Britain, Turkey and the Gulf Cooperation Council regional grouping.

The process was slowed by concerns that the coalition, recently reconstituted under US pressure, did not represent all of Syrian society, had links to extremists and did not fully subscribe to democratic principles.

“We have made a decision that the Syrian opposition coalition is now inclusive enough, is reflective and representative enough of the Syrian population, that we consider them the legitimate representative of the Syrian people,” Obama told ABC News in an interview.

Washington has, so far, only provided humanitarian, non-lethal aid to the rebels, officially declining to send arms, a position White House spokesman Carney reiterated.

The US administration made clear that it was differentiating between the Council and al-Nusra, which it sees as having extreme tendencies.

Though a minority, al-Nusra has been one of the most effective rebel groups fighting to overthrow Assad, raising concerns that hardline extremists are hijacking the 21-month-old revolt.

The front’s fighters, many of them jihadist volunteers from around the Islamic world, were instrumental in the fall of the army’s massive Sheikh Suleiman base in northern Syria on Monday after a months-long siege.

Al-Nusra has also claimed responsibility for recent suicide bombings that killed scores of people and said that it hopes to replace the Assad family’s four-decade hold on power with a strict Islamic state.

The strike on Alawites came in bomb attacks in the village of Aqrab in the central province of Hama and killed or wounded at least 125 civilians, said that the Syrian Observatory for Human Rights.

Washington also said that it was now less concerned than last week that Assad could resort to using chemical weapons stockpiles against rebels.

US Defense Secretary Leon Panetta said that Syria had not taken any new steps in recent days that signal a readiness to use its arsenal.

International military chiefs have met in London to discuss the Syria conflict, a diplomatic source said after a media reported that they discussed plans to train rebels and give air and naval support.

A British diplomatic source confirmed that the military leaders had held talks, but played down the idea that they discussed military intervention against the Assad regime.

With the total death toll from Syria’s agony now topping 42,000, according to the Observatory’s figures, the United Nations High Commissioner for Refugees said that the number of Syrian refugees in neighboring countries and the wider Arab world had now passed half a million.