Agreement was reached Wednesday on the legal status of the surface waters, Khalafov was quoted by Journal of Turkish Weekly as saying on Friday.
But the littoral states still could not agree on the legal status of the seabed.
In addition, neither the littoral states nor the international lawyers could agree on whether the Caspian Sea is a lake or sea, both legally and geographically.
"However the negotiations for details are ongoing," Khalafov said.
Issues on security, shipping, conservation of biological resources, emergencies and hydrometeorology are resolved between the Caspian littorals -- Russia, Kazakhstan, Turkmenistan, Azerbaijan and Iran.
Speaking at the second and last day of the 39th meeting of the Ad Hoc Working Group to determine the legal status of the Caspian Sea in Baku, Khalafov underlined that the first step of the final agreement has been reached.
"More than 80 percent of the final agreement is settled," the deputy foreign minister said, adding, "We believe the Astana summit will be the last meeting to reach a final agreement."
Khalafov noted that the presidential summit meeting in Astana, the capital of Kazakhstan, where negotiations on the final agreement to be held, will take place in 2016, and the next Ad Hoc Working Group will meet in Iranian capital Tehran.