Supporters and opponents of Ukrainian President Viktor Yanukovych are to hold rival protests in Kiev, amid fears of possible clashes.
Activists and opposition parties are hoping hundreds of thousands of people will take part in a "Dignity Day" rally in the central Independence Square.
Protests began last month after the president's last-minute move to pull out of a landmark deal with the EU.
Mr Yanukovych has said he fears the association and trade agreement will put at risk many enterprises dependent on trade with Russia.
The president - who says he eventually aims to sign the deal - has also admitted being under heavy pressure from Moscow, which wants Kiev to join a Russian-led customs union instead.
Several thousands pro-EU protesters remained overnight in Independence Square ahead of their rally, which is expected to start at 12:00 local time (10:00 GMT) on Sunday.
Barricades around the perimeter of the main protest encampment in the heart of the capital have been strengthened following an attempt by special police to dismantle them earlier this week.
Opposition leaders have urged protesters to remain vigilant, fearing "provocateurs" could trigger clashes between rival demonstrators.
The opposition has also accused the authorities of bussing people into Kiev for the pro-government rally and providing them with money and food.
The authorities officially deny this, but a number of participants in the rally have said they were forced to take part.
The two rival camps held demonstrations close to each other on Saturday. There were no reports of any clashes.
In a separate development, Mr Yanukovych suspended his deputy security chief and Kiev's mayor over the police violence against pro EU-protesters on 30 November.
Prosecutors are investigating Volodymyr Syvkovych and Olexander Popov - alongside another two senior officials - on suspicion of abuse of office in the crackdown.
This has energised the pro-EU protesters, who are demanding that all those involved in the clampdown be sacked and punished. They also want the government to resign.
While pro-EU protests have gripped the capital and other cities in western and central Ukraine, President Yanukovych retains support in the east and south.
However, that backing may be dwindling, correspondents say, and there have already been pro-EU rallies in the south-east.
Protesters say Mr Yanukovych's U-turn on the EU deal triggered the mass demonstration, but they now want the total "reload" of what they describe as a corrupt system of governance.
They believe signing the EU deal would root out corruption and make Ukraine's economy more open and transparent, citing as an example Ukraine's neighbours to the west who are now EU members.
However, the government and its supporters fear that economic liberalisation would hurt the country's economy, especially the industrial south-east which relies on trade with Russia.
Moscow has already put economic pressure on Ukraine, with customs delays and a ban on Ukrainian chocolates, and there are concerns it could escalate such measures if Kiev drew closer to Brussels.