Eleven Western and Arab countries denounced growing involvement in the Syrian crisis by Iran and the Lebanese Shiite militia Hezbollah, calling Wednesday for the immediate withdrawal of all foreign forces aligned with Damascus. In the so-called Friends of Syria gathering yesterday in Amman, foreign ministers denounced the recent involvement of Hezbollah forces in the western Syrian town of al-Kussair and elsewhere in the country. In a statement late Wednesday, the ministers urged an "immediate withdrawal of Hezbollah, fighters from Iran and other regime-allied foreign fighters from Syrian territory," calling their presence a "serious threat to regional stability." During the gathering, the group's third since February, the ministers outlined parameters for the formation of a proposed transitional government in Syria adopting all executive authority and extending control over the armed forces and security apparatuses. In the statement, foreign ministers expressed concern over the alleged use of chemical weapons by regime, called for a comprehensive UN probe into the question and warned of "severe consequences if these reports are confirmed." According to sources present at the closed-door meeting, ministers agreed to help lift various Western bans prohibiting the supply of arms to Syrian opposition forces, in parallel with efforts to reach a political solution to the crisis. The initiative comes amid a series of military gains by Damascus, with regime forces retaking dozens of towns and villages formerly in under opposition fighters control. German intelligence warned that Syrian government forces were gaining the upper hand over the opposition fighters, according to a Spiegel Online report. The intelligence assessment described the opposition fighters' situation as precarious and said al-Assad's army had become stronger. White House spokesman Jay Carney said he was unfamiliar with the German assessment but that the US government believed al-Assad "is significantly weaker than he was two years ago, and in that time the opposition has gotten significantly more organized." Wednesday's summit came ahead of a slated international conference next month in Geneva to launch peace talks between Damascus and opposition forces to bring an end to a conflict that has resulted in over 80,000 deaths by UN estimates. The Friends of Syria warnings over international involvement came hours after the US and Britain condemned the growing Iranian and Hezbollah roles in Syria, cautioning that their intervention may lead to region-wide sectarian strife. "The US and other countries are not sending forces to Syria - Hezbollah is," US Secretary of State John Kerry said in Amman ahead of a pro-Syrian opposition conference. British Foreign Minister William Hague accused Tehran and the Shiite group of "propping up" the al-Assad regime. German Foreign Minister Guido Westerwelle called on the European Union to declare Hezbollah, or at least its military arm, a terrorist organization. Al-Assad on Sunday denied allegations that Iran and Hezbollah are supporting his troops. Foreign ministers representing the US, UK, Italy, Germany, France, Saudi Arabia, Jordan, the UAE, Egypt, Qatar and Turkey attended the conference in the Jordanian capital, which was marked by small-scale protests by pro-Assad supporters. George Sabra, acting president of the Syrian Opposition Coalition, took part on behalf of opposition and its forces.