Salome Zurabishvili, an opposition leader, said: "The whole nation is standing here … so that the self-proclaimed president recognises that there is a crisis in this country, that there is a very serious crisis."
The protesters pressed for another meeting with Saakashvili after a month of demonstrations demanding his ouster.
Nino Burjanadze, an opposition leader, told journalists: "If we do not receive a response today and this meeting does not happen in the nearest day or two it simply means that the president does not really want dialogue."
While opposition leaders insist on Saakashvili to resign, they say they are still ready to listen to any ideas the president has for bringing the country together.
Though tensions have increased in recent days, officials have vowed there would be no repeat of November 2007 events when riot police used water cannon, tear gas and rubber bullets to disperse thousands of protesters.
The number of protesters has steadily dwindled since a peak of some 60,000 during the first days of demonstrations but the latest rally attracted the largest numbers in recent days.