"Based on the good traditions of friendship and good-neighborliness that bind Russians and Belarusians, our countries and peoples are systematically expanding mutually beneficial cooperation in all areas," the telegram on the Kremlin's website says.
Putin noted that, despite the unprecedented sanctions pressure from the outside, the countries are effectively coordinating efforts in the international arena.
Earlier, Lukashenka said that Russia and Belarus are building up the potential of the Union State based on the inseparability of interstate friendship.
TV towers in a number of cities will turn on festive lighting on Sunday, April 2, in honor of the Day of Unity of the Peoples of Russia and Belarus.
In total, 29 regions will participate in the celebration.