Viktoras Pranckietis and Inara Murniecė, as well as members of groups for Interparliamentary relations from the two neighboring countries, will join a festive procession and attend the opening of the festival near the town's wooden pier.
The opening ceremony will include the hoisting of the Lithuanian and Latvian flags and greeting speeches by the two parliamentary speakers, the Lithuanian Seimas said.
Pranckietis and Murniecė are also scheduled to visit a fair and an international exhibition, as well as to award the winners of a "brain battle" between Lithuanian and Latvian schoolchildren.
Lithuanians and Latvians celebrate the Balts' Unity Day to commemorate the defeat of the Livonian Brothers of the Sword in the Battle of Saulė on September 22, 1236.
Lithuanian and Latvian cities and towns have taken turns to host the celebrations after the parliaments of the two countries designated September 22 as the Balts' Unity Day in 2000.