BEIRUT (Reuters) - The US mediator in talks to resolve the maritime border dispute between Israel and Lebanon said on Friday that negotiations had made "very good progress", but more work was needed to reach a final agreement. The two countries are engaged in US-brokered negotiations to delineate a common maritime boundary, which would help identify each aspect of oil and gas resources and pave the way for further exploration. Amos Hochstein arrived in Lebanon on Friday morning for a whirlwind round of talks with senior officials, including the president, prime minister, parliament speaker and deputy, as well as security officials. "I think we are making very good progress," he said after meeting with Lebanese President Michel Aoun, Parliament Vice President Elias Bou Saab and Director General of Public Security Abbas Ibrahim. But he said later, before leaving Beirut airport, "I am very hopeful, but more work needs to be done." Hochstein's last visit to Beirut was in late July for meetings with Lebanese officials. After that visit, he said, "I look forward to being able to return to the region to make the final arrangement." At the time, a senior Israeli official told Reuters that the government would present a new Israeli proposal that "contains a solution that would allow the Lebanese to develop gas reserves in the disputed area while preserving Israel's commercial rights." A Lebanese official also clarified at the time that the proposal would allow Lebanon to drill in the entire Qana area, an area that could contain hydrocarbons and go beyond Line 23. Line 23 is the maritime line that Lebanon initially set during the negotiations to represent its borders, before increasing its demands to a line further south. The exploration rights south of Line 23 would represent a concession from Israel