"There is no legal foundation" for the expulsion, Archbishop Kliment, a spokesman for the church, told AFP in the monastery.
The monks are members of the Ukrainian Orthodox Church, which was under the authority of the Russian Orthodox Church.
After Russia invaded Ukraine last year, the Church broke off links with Russian Patriarch Kirill -- a supporter of the war.
But Ukraine's government believes it is still de facto dependent on Moscow.
The cave monastery, which overlooks the Dnipro River, was founded in the 11th century and is a UNESCO World Heritage site.
"Our Church was the first of Ukraine's religious organizations to condemn (Russian President Vladimir) Putin's war on Ukraine," Kliment said.
"It has given its blessing to the Ukrainian army to defend the motherland," he said.
But the government earlier this month said it was evicting the Church, citing "violations" of state property rules.
The spokesman said there was now a threat of "forced expulsion" and cut-offs of electricity, water and internet.
"We will stay in the Lavra as long as physically possible," he said.
'No link' with Moscow
In a video message on Wednesday, Metropolitan Pavlo, who is the director of the Lavra, called on the faithful to "defend this holy place with us".
Kliment said that more than 200 monks and 300 students live on the site, filled with golden domed churches with green roofs and covering an area of over 20 hectares (nearly 50 acres).
In front of one of the buildings on Friday, AFP journalists saw a removals truck in which young men were putting boxes full of books and small items of furniture.
At the main entrance, police were checking cars and asking drivers to open their boots.
At the end of last year, Ukrainian authorities raided several Church buildings including the Lavra and sanctioned clergy accused of taking pro-Moscow positions.
The Church's spokesman said he had "received information that police have the order to stop all cars carrying believers into the Lavra and check passengers before letting them in" on the eviction day.
Arina Lazurenko, 37, who came especially from the Sumy region in northeast Ukraine to visit the monastery, said she supported "all those who want to defend the Lavra and the rights of the faithful".
"I hope everything will go well," she said.
A tearful Anna, 46, said there was "no link between this Church and Moscow".
"It's a lie," she said, adding that she would "do her best" to come and pray on Wednesday to defend the Church.
© 2023 AFP