Syrian opposition urges world leaders to take action on regime's use of chemical weapons

En esta foto del 22 de septiembre de 1973 se ve el minarete de la mezquita Umayad en Alepo, Siria. La prensa estatal siria y activistas opositores dijeron que el minarete fue destruido, aunque las dos partes lo atribuyen a sus adversarios (AP Foto/Azad, Archivo) (The Associated Press)

This March 6, 2013 citizen journalism image provided by Aleppo Media Center AMC which has been authenticated based on its contents and other AP reporting, shows the minaret of a famed 12th century Umayyad mosque before it was destroyed by the shelling, in the northern city of Aleppo, Syria. The minaret of a famed 12th century Sunni mosque in the northern Syrian city of Aleppo was destroyed Wednesday, April 24, 2013. President Bashar Assad's regime and anti-government activists traded blame for the attack against the Umayyad mosque, which occurred in the heart Aleppo's walled Old City, a UNESCO World Heritage site.(AP Photo/Aleppo Media Center, AMC) (The Associated Press)

Esta imagen tomada de video obtenido del Aleppo Media Center AMC, el cual ha sido autentificado con base en su contenido y otros reportes de la AP, muestra la famosa mezquita Umayyad del siglo XII, la cual fue dañada por bombardeo, en el norte de la ciudad de Alepo, Siria, el miércoles 24 de abril de 2013. (Foto AP/Aleppo Media Center, AMC) (The Associated Press)

Syria's main Western-backed opposition is calling on the international community to act "urgently and decisively" on President Barack Obama's public assertions that Syria's use of chemical weapons would cross a "red line."

The White House and other top Obama administration officials said Thursday that U.S. intelligence has concluded with "varying degrees of confidence" that the Syrian government has twice used chemical weapons in its civil war.

A coalition statement called on the world community to prove to the Syrian regime that the statements about crossing a red line were not just "empty words."

It said failure to act will be seen by the regime as a green light to use chemical weapons on a larger scale in the future.