Ukrainian President Viktor Yanukovych said on Monday he would enter talks to end anti-government protests that have paralyzed the country for weeks.
In a statement on his website, Yanukovych made the surprise announcement that he had agreed to sit down with three former Ukrainian leaders on Tuesday with the aim of finding a "compromise" to end the crisis.
The opposition is calling for Yanukovych's ouster after he shelved a treaty with the European Union to focus on strengthening ties with Russia.
Meanwhile, U.S. film star George Clooney issued a message in support of the "brave" Ukrainian protesters.
"Let me just say this to all you in the square in Kiev or all around Ukraine: When you look to the West, know that we are looking back at you with great admiration," Clooney, who has campaigned for issues like as same-sex marriage in the U.S. and raised awareness for ethnic cleansing in Darfur, said in a video posted on Monday.
"We here in the United States have great affinity with those seeking democracy...true democracy cannot exist without a free and fair and honest election.
"We wish you a peaceful and safe mission, we wish you the government that you want, and we wish you the strength to carry on. Good luck."
Sunday saw the largest demonstration in the country since the 2004 pro-democracy Orange Revolution protests that annulled Yanukovych's presidential victory due to voting fraud.
Hundreds of thousands of anti-Yanukovych protesters poured into the streets, toppling a statue of former Soviet leader Vladimir Lenin and blockading government buildings, according to The Associated Press.
A court has ordered protesters occupying the city hall in the capital Kiev to leave the building by Monday. As the deadline arrived, riot police flooded the streets and surrounded site. Protesters, meanwhile, barricaded themselves inside, arming themselves with wood planks, metal rods and bottles of sunflower oil, hoping to make riot police slip if they advanced, with the AP said.
Vitaly Klitschko -- a champion boxer turned opposition leader -- told Reuters that demonstrators must stand firm.
"The opposition must stay here and do everything to stop the police from breaking up a peaceful demonstration," he said, while calling on elderly or frail people to go home.
"We won't let anybody into the building," Vasyl Khlopotaruk, one of the organizers, told the AP. "But we hope there isn't bloodshed."
Amid heavy snowfall in the square outside, black-robed Orthodox priests sang solemn prayers for peace.
Opposition leader Arseniy Yatsenyuk called for calm, telling several thousand protesters that police were ordered not to storm the building, but to blockade the protest camp to deplete it of food and other amenities.
With Yanukovych saying on his website that he supported a request to enter talks, E.U. Commission President Jose Manuel Barroso dispatched foreign policy chief Ashton to Kiev.
The Associated Press and Reuters contributed to this report.