The UN Security Council has adopted a resolution calling on Syria to forge formal ties with Lebanon and demarcate the border between the two countries.
Much of the Syria-Lebanon border is unmarked
The 15-member council adopted the resolution by 13-0 with Russia and China abstaining.
Resolution 1680 seeks full implementation of a 2004 resolution urging a complete end to external influence in Lebanon.
It was co-sponsored by the United States, France and Britain.
In 2005, Syria withdrew its troops from Lebanon following 29 years of military and political rule over its smaller neighbour, in line with Resolution 1559 of 2004.
The move came after Damascus faced massive international pressure following the assassination of ex-Lebanese PM Rafik Hariri, in a bombing with which it denied any connection.
However, it has so far refused to formalise diplomatic contacts with Lebanon or open a Syrian embassy in Beirut.
The Syrian authorities have detained seven opposition and human rights activists in recent days, including signatories of a petition calling for improved Syrian-Lebanese relations.
Hundreds of Syrian and Lebanese intellectuals signed the petition which was published last week in an anti-Syrian newspaper in Lebanon.
On Sunday the authorities arrested Michel Kilo, a prominent writer and democracy advocate, who signed the petition.
The National Organisation for Human Rights in Syria said it is expected that he will face serious charges that could result in a life sentence.
Mr Kilo is accused of "provoking religious and racial dissent, publishing false and exaggerated information aimed at harming the state's reputation and libelling the head of state and state courts", the organisation said in a statement quoted by AFP news agency.
Wednesday's Security Council resolution "strongly encourages" Syria to "respond positively to the request made by the government of Lebanon ... to delineate their common border".
It also urges the establishment of "full diplomatic relations and representation".
Such a move would constitute a "significant step toward asserting Lebanon's sovereignty, territorial integrity and political independence," the text says.
But both Russia and China abstained from the vote. They believe the resolution is unnecessary and would constitute UN interference in bilateral Lebanese-Syrian relations.
The Syrian foreign ministry described it as provocative and biased in a statement issued shortly after the vote.
"Resolution 1680 marks a new precedent in international relations in terms of interference in countries' internal affairs and the bilateral relations between them," it said.