KIEV, Ukraine — Ukrainian riot police moved methodically around the periphery of the sprawling protest camps here Monday, away from the focus of attention, the occupied Independence Square.

They removed barricades on side streets, dismantled tents and calmly moved groups of protesters away from buildings of the national government. One police unit — it isn’t clear which agency it was from — raided the headquarters of the opposition Fatherland party on a quiet street in the lower part of the capital city, seizing and smashing computer equipment.

They were either tightening the noose around the many thousands of Ukrainians who have flocked to Kiev to express their anger over the government’s decision to back out of an agreement with the European Union in favor of closer economic ties with Russia, or their commanders hadn’t yet decided whether to attack the demonstrators head on.

Police put pressure on the protesters, but plenty of pressure already was on President Viktor Yanukovych, who made the decision to spurn the E.U.

He agreed to meet Tuesday with Ukraine’s three ex-presidents, who want to see if they can thrash out a solution to the crisis that has gone on for more than a week and that they believe threatens to spin out of control.

Catherine Ashton, the E.U.’s foreign policy chief, is to arrive here Tuesday to counsel a peaceful solution.

And, to add to the impression that the whole world is watching, Vice President Biden called Yanukovych on Monday to warn against the growing threat of violence, according to a statement issued by the White House. Biden urged Yanukovych to de-escalate the situation immediately and enter into talks with opposition leaders, the statement said.

Biden told Yanukovych that Victoria Nuland, assistant secretary of state, will return to Kiev to make the American position clear. She was here late last week, telling the opposition to work within the law and telling Yanukovych to deal in good faith with the opposition. She was in Moscow during the weekend, discussing Ukraine, among other topics, with Russian leaders.

The Ukrainian president suggested on his Web site that he would be open to roundtable talks with opposition leaders. But they derided the proposal as insincere.

A television station here was briefly attacked by a small mob of men thought to be in the employ of the police. Another TV station, Hromadske TV, saw its Web site come under a cyberattack, which it later said had been traced to Krasnoyarsk, a city in Russia.

As of late Monday evening, police had not moved to enforce a court-ordered eviction notice on protesters who have occupied city hall for more than a week, using it as a headquarters and dormitory. The occupiers expected the police to storm the building, on Kiev’s main street, Khreshchatyk, just a few blocks from Independence Square. But all evening, protesters continued to move in and out of the building undisturbed.

Police officials talked tough all day, and busloads of armored police troops took up positions on the outskirts of the big square, but their interactions with the crowd were conversational and unaggressive.

Opposition leaders talked tough, too. Vitali Klitschko, the boxer turned politician, said Yanukovych would have blood on his hands if police attacked the demonstrators.

A new factor is the weather. The winter’s first serious snow dropped on Kiev through the afternoon, followed by a slicing wind as darkness fell. More snow is predicted for Tuesday, with temperatures expected to top out at 16 degrees. Ukrainians are no strangers to winter, but the weather will be another variable in everyone’s calculations.

On Monday evening, the protesters at Independence Square were busily clearing their unusually well maintained campsite of snow. Some shovelers built neatly squared off walls of snow. At the entrances, earnest young men checked all who entered, escorting away anyone who looked like a drunk or a provocateur.

Yanukovych risks looking weak to some if he doesn’t move to end the protests. But the protesters are betting that the system, in the end, will lack the will to strike against them.