The United States late Sunday declared its support for the united Syrian opposition after various groups opposed to the government of President Bashar al-Assad decided to come together following talks in Doha, Qatar.
"We look forward to supporting the National Coalition as it charts a course toward the end of Assad's bloody rule and the start of the peaceful, just, democratic future that all the people of Syria deserve," State department deputy spokesman Mark Toner said in a statement.
Britain hailed the agreement as an "important milestone in forming a broad and representative opposition that reflects the full diversity of the Syrian people."
Qatar, which along with neighbouring Saudi Arabia, has been a leading champion of the Syrian opposition, has already said it is ready to recognise a provisional government that the National Coalition plans to form.
Meanwhile, Israeli troops fired tank shells into Syria yesterday, confirming "direct hits" on the source of a mortar round that struck the Golan Heights as tensions flared along the ceasefire line.
The exchange marked the second straight day that Israeli troops have been drawn into the Syrian conflict and came just hours after an appeal for restraint from all sides by UN chief Ban Ki-moon.
On Sunday, Israeli troops fired a warning shot across the UN-monitored ceasefire line in response to Syrian fire, in the first instance of Israeli fire directed at the Syrian military in the Golan Heights since the 1973 war.
Syrian aircraft bombed the strategic border town of Ras al-Ain yesterday, killing at least four people and sending panicked residents fleeing into Turkey, an AFP photographer reported.
The blast killed four Syrians and wounded scores of others, around 20 of them seriously, according to the Anatolia news agency.
The Observatory said 12 people were killed in a blast in Ras al-Ain, although it could not immediately say if it was the same bomb.
The dead included five civilians and seven rebels -- mostly loyalists of the jihadist Al-Nusra Front, said the watchdog which bases it casualty tolls on a network of doctors and activists in civilian and military hospitals.
Syrian forces and rebels have been involved in furious fighting in the area during the past week, sending 9,000 Syrians fleeing into Turkey in the space of just 24 hours.
A total of 120 people were killed in violence on Sunday, bringing to more than 37,000 the number killed since March last year, the Observatory said.