Lebanese President Michel Aoun on Thursday signed a letter approving a landmark US-brokered agreement laying out the country’s maritime boundary with Israel, Lebanon's top negotiator, Elias Bou Saab, told reporters.
Israel was set to follow suit in approving the deal.
The agreement opens the way for offshore energy exploration and removes one source of potential conflict between Israel and Hezbollah and could help east Lebanon's financial and economic crisis.
Speaking from the presidential palace, Bou Saab said the agreement marked the beginning of "a new era" and that the letter would be submitted to US officials at Lebanon's southernmost border point of Naqoura later on Thursday.
The deal will be signed separately in Jerusalem by Israeli Prime Minister Yair Lapid following his cabinet's approval.
"The agreement... will take the form of two exchanges of letters, one between Lebanon and the United States, and one between Israel and the United States," said Stephane Dujarric, spokesman for the UN Secretary General.
Asked what happens in case of a violation by either of the sides, which remain technically at war, US envoy Amos Hochstein said the US would remain a guarantor to help resolve any disputes.
"If one side violates the deal, both sides lose," Hochstein told reporters.
Israeli Prime Minister Yair Lapid on Thursday claimed Lebanon de-facto "recognizes" the Jewish state.
"This is a political achievement -- it is not every day that an enemy state recognizes the State of Israel, in a written agreement, in front of the entire international community," Lapid said.