The vote Thursday comes after this week's attempts to arrest former Georgian president Mikheil Saakashvili, who has become a high-profile anti-corruption campaigner in Ukraine. "They have detained Mikheil Saakashvili", and called for his supporters to protest.
Saakashvili had been taken into custody on Tuesday, but a crowd of supporters freed him from a police van and swept him away.
Television footage showed a large number of police in riot gear outside the centre and a few dozen protesters, but the situation appeared relatively calm.
In a televised briefing on Wednesday, Saakashvili - supporters see him as a fearless crusader against corruption - said he would not present himself to law enforcement officials, as requested by the General Prosecutor's office.
But the two men fell out, and Saakashvili resigned from his post past year, accusing Poroshenko of corruption and blocking reforms. "If he flees from the investigation, this undermines his credibility", he said.
The lawyer said his defendant would object to force-feeding and would continue striking if a court decides to keep him behind bars for 60 days.
Zaal Udumashvili, UNM's candidate in the October mayoral elections in Tbilisi, addressed the protesters as well, saying the rally was named the March of Dignity, "since it is exactly a matter of our dignity to express loud protest about the ongoing processes in Ukraine and Georgia". In July, Poroshenko stripped Saakashvili of the Ukrainian citizenship he received on becoming governor, opening up the possibility of Saakashvili's deportation back to Georgia, where he was wanted on charges of abuse of power.
"I had a constructive and open discussion with President Poroshenko on Ukraine's efforts to fight corruption", Lagarde said in a statement.