The incident which took place in the Kerch Strait on November 25 closes all political discussion about whether Kyiv should denounce its 2003 agreement with Russia on cooperation in the use of the Sea of Azov and the strait, Yevhen Marchuk, Ukraine's representative in the Trilateral Contact Group (TCG) which mediates the Donbas conflict, said.

"Today I don't even see a subject matter for discussion: to denounce or not to denounce the 2003 agreement with Russia on the joint use of the Sea of Azov and the Kerch Strait... Russia crossed out this agreement, and the one on [joint] national border," Marchuk said at a panel discussion during the second international maritime security conference in Kyiv on Thursday.

"The only platform where Ukraine and Russia could discuss the current situation is the Normandy Four which met more than a year and a half ago," he said.

Ukraine will continue to insist on the creation of a TCG subgroup on border issues to discuss the waters of the two seas, but Russia is opposed to the idea, Marchuk said.

"Russia is categorically against the creation of a separate working group on border issues. And now it is clear [why]: because the Sea of Azov, too, is a border," he said.