BEIRUT - Syria’s exiled opposition has for the first time agreed on the concept of dialogue with the regime, while maintaining its insistence on President Bashar al-Assad’s ouster, ahead of key US-Russian talks on the Syrian conflict. Key Assad backer Moscow and opposition supporter Washington have increased pressure on the rival parties to moderate their stand and reach a political solution to the 22-month conflict.

On Thursday, the opposition Syrian National Coalition declared at a meeting in Cairo that it welcomed “any political solution or international effort” aimed at Assad’s departure. The stand came after its leader Moaz al-Khatib’s surprise announcement that he was ready for “direct discussions with representatives of the Syrian regime”.

Analysts say the SNC had to keep up its insistence on the departure of Assad or risk losing support on the streets, but leading dissidents have also started to lose hope in a military solution.

The United States said Iran is stepping up its support for the Syrian regime and that Russia is still arming it, heightening fears on Friday that the conflict may spill over the country’s borders.

The assessment by US Secretary of State Hillary Clinton came as US Vice President Joe Biden prepared to discuss the crisis with Russian Foreign Minister Sergei Lavrov and Syrian opposition chief Moaz al-Khatib.

Fresh concerns about the 22-month conflict drawing in the wider region arose after Damascus threatened to retaliate over a reported Israeli air raid and key ally Iran warned the attack would have “grave consequences.”

President Bashar al-Assad’s regime accused Israel of sending its warplanes to attack a military research centre in Jamraya, near Damascus, on Wednesday. Israel has so far maintained a stony silence, as well as over separate reports its aircraft had hit a weapons convoy near the Lebanese border. But Israeli media speculated that the alleged air strike on the convoy could spark a chain reaction, and reported troops on high alert in northern Israel.

Israel has frequently warned that if Syria’s chemical weapons fall into the hands of Lebanon’s movement Hezbollah, Israel’s arch-foe and close Damascus ally, this would be a casus belli. Israel has also raised the alarm over long-range Scud missiles, anti-aircraft systems and surface-to-surface missiles being transferred to Hezbollah.

Residents of eastern Lebanon, meanwhile, said soldiers and unidentified gunmen clashed near the border with Syria on Friday, as a security official said at least five soldiers and a wanted gunman were killed.

UN chief Ban Ki-moon called on all parties to “prevent tensions or their escalation in the region,” as Hillary warned of “the dangers of an increasing civil war and a potential proxy war.” “The worst kind of predictions of what could happen, both internally and spilling over the borders of Syria, are certainly within the realm of the possible now,” she said.

World leaders, ministers and top military brass kick off three days of talks at the Munich Security Conference later on Friday with the spotlight on Syria, Mali and Iran.

US Vice President Joe Biden will be among the line-up and kicked off a three-nation European tour warning Iran that the opportunity for talks with the West over Tehran’s contested nuclear programme was not open-ended. A day after meeting Chancellor Angela Merkel in Berlin, freshly-inaugurated Biden is due to address participants in Munich on Saturday and turn his attentions to Syria amid fears the conflict may spill over the country’s borders.

He is scheduled to meet Russian Foreign Minister Sergei Lavrov and Syrian opposition chief Moaz al-Khatib, and also see UN-Arab League envoy to Syria Lakhdar Brahimi in the southern German city, the White House said.

In Geneva, the UN’s children’s agency said some 420,000 people - half of them children - in the central region of Homs desperately need humanitarian aid.

On the ground, southern Damascus saw fresh clashes on Friday, while army shelling hit a town in northern Aleppo province and Homs city was also pounded, the Syrian Observatory for Human Rights said. At least 163 people were killed nationwide on Thursday, the watchdog said.