A dangerous border row looms between Ukraine and Russia as relations plunge to a new low. The Kremlin says Kiev’s hint that it will review the status of key a Russian naval base in Ukraine could call into question the whole treaty signed between the two countries after the fall of the Soviet Union.Russian Defence Minister Sergei Ivanov said: “The agreement on the Black Sea fleet is one part of the bilateral treaty. The second part contains the mutual recognition of borders. Any attempt to revise the treaty would be fatal.” The row erupted when the Russian monopolist Gazprom demanded that Ukraine pay almost five times more for its gas than it currently does. Kiev hit back by suggesting it might reconsider the terms of the lease on the Sevastopol base in the Crimean peninsula.