"A large police force will be on duty during the event and will be ready to help," Pozela told a news briefing.
"There will be uniformed and plain-clothes police officers, as well as mounted police and canine handlers," he said.
Saulius Gagas, the Vilnius county police chief, said police officers from other districts would be brought in to assist the capital's force.
When asked how many officers would be on duty during the march, he said, "That number is not being disclosed for tactical reasons, but there will be as many as are needed."
The organizers have said they expect 7,000 people to take part in the march, but the police believe there will be more of them.
The organizers say the Family Defense March is a rally against the Istanbul Convention and other initiatives "directed against the traditional family".
They say the ruling bloc's proposals, such as the one to introduce "the concept of social gender" in school curricula, run counter to the constitutional principle that parents have the right to bring up their children according to their convictions.
The organizers say the march will set off in Klaipeda and will be joined on its way to Vilnius by people from all over Lithuania. The marchers will gather in the capital's Vingis Park for a rally scheduled to start at 6 p.m.
Raimondas Grinevicius, a former member of the Order and Justice Party, is the initiator and leader of the march. Other organizers include Arturas Orlauskas, a comedian, Algimantas Rusteika of the National Alliance, and Arvydas Daunys, head of the Infa.lt website.
The Family Defense March has prompted social media initiatives to hold counter-rallies in the park in support of the LGBT community.