Western and Arab countries opposed to President Bashar al-Assad have agreed at talks in Qatar to give urgent military support to Syrian rebels fighting for his overthrow.
Ministers from the Friends of Syria group also condemned the Syrian government for its use of Iranian and Hezbollah fighters, and demanded that they withdraw immediately.
Guerrillas from Lebanon's Hezbollah organisation spearheaded the recapture of the strategic border town of Qusair from mainly Sunni Muslim rebels two weeks ago.
Iraqi gunmen have also been fighting around the shrine of Sayyid Zainab south of Damascus, while Iranian military commanders are believed to be advising Assad's officers on their counter-offensives against the rebels.
The ministers said the growing sectarian nature of the conflict and the foreign interventions threaten the unity of Syria and broaden the conflict across the region.
More than 90,000 people have died in more than two years of fighting.