DAMASCUS - Syrian President Bashar al-Assad warned on Thursday that the security situation in Lebanon was "fragile" and urged Beirut to combat foreign-backed extremism in the north of the country.

"Anything positive in Lebanon would be worthless without a solution to the problem of extremism and salafists in northern Lebanon who are officially supported by some countries," he said, without naming them.

"The situation in Lebanon is still fragile," the Syrian leader said at a four-way summit in Damascus.

"We are worried about what is happening in Tripoli," he told French President Nicolas Sarkozy, Turkish Prime Minister Recep Tayyip Erdogan and Qatar's emir, Sheikh Hamad bin Khalifa al-Thani.

At least 23 people have been killed since violence erupted in May in Tripoli between backers of the Lebanese opposition and the majority in Lebanon's parliament.

Lebanese army troops have rarely intervened in the clashes.

Assad said he had asked Lebanese President Michel Sleiman, the former army chief of staff who visited Damascus in mid-August, to "urgently send more troops to the north" of the country.

"The presence of the army is a must to tackle the problem. Lebanon will not see stability with the existence of extremism," he added.

Assad sees full ties with Lebanon by year-end

Assad said on Thursday that he expected Damascus to establish full diplomatic relations with Beirut by the end of this year.

Syria and Lebanon announced on August 13 their intention to open diplomatic ties for the first time since independence some 60 years ago -- following up on a pledge made by Assad and Lebanese President Michel Sleiman in Paris in July.

"The diplomatic exchange was decided on during the summit in August and now we are in the process of legal procedures," Assad said, referring to his meeting with Sleiman during his visit to Damascus.

"Ambassadors are likely to be exchanged by the end of this year," he added. -Agencies