Angry demonstrators gathered across the country to denounce President Viktor Yanukovych's turnaround, urging him to change his mind and sign the deal at a summit in Vilnius, Lithuania, scheduled for next week.
An opinion poll conducted in October found that 45 percent of Ukrainians favor stronger ties with the EU, 14 percent favored an economic alliance with Russia, while the rest were either against any alliances or were undecided. The GFK Ukraine polling agency, that conducted the research, said the poll questioned 1,000 people and its margin of error was 3 percentage points.
"We will show the authorities that they cannot ignore the choice of the majority of people," said Vitaly Klitschko, an opposition leader and former world heavyweight boxing champion.
Klitschko urged Ukrainians to turn out for the Sunday rally. "We will show them that together we are a force that can win."