Washington has asked Syrian opposition representatives not to respond to the provocations of the regime after helicopters dropped barrel bombs on opposition areas in the country’s southwest. The US hopes for a “diplomatic solution” that protects the de-escalation agreement brokered last year by Washington, Moscow and Amman. Diplomatic sources said that US President Donald Trump and his Russian counterpart Vladimir Putin will discuss the Syrian regime offensive in the South during an expected summit in Vienna as part of the US leader’s European tour next month. In a written letter addressed to the armed opposition, Washington wrote: “We are currently working on protecting the truce using diplomatic channels, and we are exerting important efforts to achieve that.” The letter also stressed the need “not to respond to provocations, because such behaviors would only speed up the worst scenario for the south of Syria and would undermine our efforts.” A copy of the letter, which was received by Asharq Al-Awsat, also noted: “The regime is trying to provoke you through barrels and statements, searching for a pretext to attack the South. We cannot offer them this excuse.” On Friday, the Syrian Observatory for Human Rights said Syrian regime helicopters dropped more than 12 barrel-bombs on rebel-held territory in Daraa for the first time in a year, causing damage but no deaths. Head of the Syrian regime Bashar Assad had pledged to recuperate the area, located at the border with Jordan and the Israeli-occupied Golan Heights. On Thursday, the US State Department warned of "serious repercussions,” if the Syrian regime continues to violate the southwest de-escalation zone. Meanwhile, at least one Syrian soldier was killed and seven others wounded in a US-led coalition strike in central Syrias Homs province late Thursday, according to the Observatory.