Leonid M. Kravchuk, Ukraine’s president from 1991 to 1994, issued his warning while offering his services to Parliament in mediating negotiations between the government and opposition leaders on overhauling the Constitution to weaken the power of President Viktor F. Yanukovych.
But Parliament halted work for the evening without voting on the constitutional change or another measure to assuage tension.
President Vladimir V. Putin of Russia had told European Union leaders at a summit meeting Tuesday in Brussels that his government intended to fulfill its financial aid commitments to Ukraine in spite of negotiations here that could put a pro-Western government in power.
Mr. Putin said the $15 billion aid package was for the Ukrainian “people.”
But that stance was reversed at a cabinet meeting in Moscow on Wednesday, where Mr. Putin brought up the subject of the aid, saying, “I ask the government to carry out these agreements in full.”
But his prime minister, Dmitri A. Medvedev, suggested that it would be reasonable to fulfill the agreements “only when we know what economic policies the new government will implement, who will be working there, and what rules they will follow.”
Mr. Putin quickly agreed, saying, “That’s reasonable.”
A report by the Itar-Tass news agency said this indicated a decision to halt the aid, meaning Ukraine would not receive a $2 billion payment expected by Friday.
Political commentators said there were other signs that Russia was raising the economic pressure on Ukraine, seemingly to discourage Mr. Yanukovych from compromising with the opposition.
Echoing statements made in 2006 and 2009 before shipments of natural gas to Ukraine were stopped, a deputy director of Gazprom, the state-owned natural gas export monopoly, said Ukraine had failed to make payments on a $2.7 billion debt.
Russian customs officials began heightened checks on trucks crossing the border from Ukraine, and an association of Ukrainian truckers told members to expect delays of 10 to 15 working days.
Standard & Poor’s, the ratings agency, on Tuesday downgraded Ukraine’s sovereign debt, citing political uncertainty and the prospect that the protests would succeed in installing a pro-Western government, resulting in a probable cancellation of the Russian financing that was suspended Wednesday.
Without Russian aid or a Western substitute, Ukraine will be forced to default on its debt or devalue its currency, the hryvnia.
After five people were wounded on Wednesday in fighting between two factions of antigovernment protesters inside one of the city’s occupied government buildings, protest organizers announced the formation of an umbrella command for street bands, to be called a National Guard.
The scuffle came as the opposition’s more moderate political leadership faced pressure to demonstrate greater control on the streets, in exchange for concessions from the government.
Parliament on Wednesday passed an amnesty bill covering protesters arrested in clashes with the police that will take effect only after protesters leave occupied administrative buildings.
Members of the nationalist party Svoboda fought to eject activists from a group called Common Cause from the main building of the Agriculture Ministry, then both factions left the building, allowing the police to again guard the upper floors.
The move appeared to represent a concession from the opposition, after Ukraine’s prime minister, Mykola Azarov, resigned on Tuesday.
The fighting among protesters inside, though, had been intense.
It involved so-called traumatic guns, or nonlethal pistols firing rubber bullets.
Afterward, the stairs were slicked with water from the building’s firefighting system, apparently also used in the melee, and broken glass and furniture littered the halls.
Protesters for weeks had suspected that the government was using location data from cellphones near the demonstration to pinpoint people for political profiling, and they received alarming confirmation when a court formally ordered a telephone company to hand over such data.
Earlier this month, protesters at a clash with riot police officers received text messages on their phones saying they had been “registered as a participant in a mass disturbance.”
Then, three cellphone companies — Kyivstar, MTS and Life — denied that they had provided the location data to the government or had sent the text messages.
Kyivstar suggested that it was instead the work of a “pirate” cellphone tower set up in the area.
In a ruling made public on Wednesday, a city court ordered Kyivstar to disclose to the police which cellphones were turned on during an antigovernment protest outside the courthouse on Jan. 10.
The order applied only to this one site on one day, and did not cover the area of the main protest, Independence Square, where sometimes more than 100,000 people have shown up, most presumably carrying cellphones whose location there could identify them as political opponents of the government.
Source: The New York Times