The U.N.-Arab League envoy to Syria ended his days-long visit to Damascus on Friday, calling on both the government and the opposition to attend a peace conference in Geneva later this month but acknowledging the gathering cannot take place if the opposition refuses to take part.

Lakhdar Brahimi, who had travelled to Damascus at the end of a Mideast tour to muster regional support for the conference, appeared uncertain about prospects for the meeting.

“We will say it’s happened only when it happens,” he told reporters at a press conference in Damascus, urging both sides to cooperate.

Mr. Brahimi’s plea came just hours after officials said Israeli warplanes had attacked a shipment of Russian missiles inside a Syrian government stronghold a development that threatened to add another volatile layer to regional tensions from the Syrian civil war.

An Obama administration official confirmed the Israeli airstrike late Thursday, but provided no details. Another security official said the attack occurred late Wednesday in the Syrian port city of Latakia and that the target was Russian-made SA-125 missiles.

Both officials spoke on condition of anonymity because they were not authorised to publicly discuss the attack. There was no confirmation from Syrian officials, and state media made no mention of the reports.

Mr. Brahimi warned that if the crisis goes on, expectations are that those directly affected by the crisis may reach half of Syria’s total pre-war population of 23 million people.

“It is time for Syrians to cooperate and for others in the region and outside to cooperate with them to end this crisis,” Mr. Brahimi said.

The envoy, who met this week with Syrian President Bashar Assad and Damascus-based opposition groups, said the Syrian government has confirmed it would attend.

Deeply fractured Syrian opposition groups are also split on whether to attend the Geneva talks. They also disagree over conditions for taking part from demands that Assad step down right away to guarantees that he would not be part of a negotiated solution for the country’s future

This time, Mr. Brahimi appeared to put the onus on the opposition, saying talks in Geneva cannot “go forward without the opposition”.

“The participation of the opposition is essential, necessary and important,” he said.

Syrian troops capture key town

Meanwhile, Syrian state TV and opposition activists said the Army has captured a strategic town in northern Syria believed to be the home of a chemical weapons production facility and storage sites.

The town of Safira has been the scene of three weeks of intense fighting as the army kept trying to retake it from rebels who have been in control there for more than a year.

Although unconfirmed, Safira is believed to be one of two sites that chemical weapons inspectors were unable to visit because of security concerns.

The town is also strategic as a supply route for Syrian government forces in the contested city of Aleppo.

Syrian activists in Aleppo province confirmed Friday that rebels withdrew from Safira overnight under heavy fire, leaving it to government troops.

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