U.S. Air Force strikes on the Syrian territories may start from this Thursday, according to the American NBC News channel quoting a U.S. government source on Tuesday.

U.S. Air Force strikes on the Syrian territories may start from this Thursday, according to the American NBC News channel quoting a U.S. government source on Tuesday.

The source told the channel that strikes may last for three days, they will be limited and targeting specific points.

Earlier, sources said that the Western powers had informed the Syrian opposition that a blow will be launched against the Syrian army within days, according to sources attending a meeting between Western envoys and representatives of the Syrian National Coalition held in Istanbul.

"The Syrian opposition had received clear assurances that an operation, intended to prevent the regime of Bashar al-Assad to use chemicals anew, will take place during the coming days," a source told Reuters news agency Tuesday.

"They (Western countries) will continue its preparations for the Geneva negotiations," Reuters added.

A meeting was held in a hotel in central Istanbul and attended by senior representatives of the Syrian opposition, including the head of the Syrian National Coalition Ahmad Jarba, and envoys from 11 countries of the so-called 'Friends of Syria' group, including the U.S. ambassador to Syria Robert Ford.