A planned visit by a Lebanese delegation to Damascus this week was on Monday cancelled by Syria's government, Reuters has reported.
The meeting had been set up to discuss delineating the two countries shared maritime border.
But on Monday the Syrian government sent a letter to the Lebanese Foreign Ministry saying "the time was not right" for such a visit, the agency reported a diplomatic source as saying.
The cancellation came shortly after Lebanon's President Michel Aoun announced in a tweet that deputy speaker of parliament Elias Bou Saab would lead the delegation to Syria on Wednesday to start the talks.
A dispute over the sea boundary broke out last year after Syria granted a licence to a Russian energy company to begin maritime exploration in an area claimed by Lebanon. Several gas discoveries have been made in the eastern Mediterranean.
The talks were due to begin only days after Lebanon and Israel reached a historic agreement to delineate their boundaries after years of US mediation. Both countries are still technically at war and the US acted as the go-between in the talks that paved the way for oil and gas exploration in the now-mapped portion of the sea.