KIEV, Ukraine - Viktor Yanukovych, the president of Ukraine, went on sick leave Thursday, leaving negotiated efforts to resolve the country’s political crisis hanging.

A statement on the president’s website said Yanukovych, 63, was taking time off because of a respiratory illness and fever. It offered no indication of how long he was expected to be absent. The statement was attributed to a deputy director of the presidential department for medical affairs.

Yanukovych has faced pressure from Russia to take a harder line with protesters opposing his government, rather than continue negotiations that could lead to his ceding some power to pro-Western members of the opposition.

Yanukovych went on leave without signing into law a bill repealing the harsh restrictions on freedom of speech and assembly that were enacted this month. The repeal was passed by the parliament on Tuesday with support from the pro-government Party of Regions, a significant concession to the opposition but one that means little unless the president signs it. The prime minister, Mykola Azarov, also resigned Tuesday.

The developments followed negotiations in the parliament between opposition leaders and the government over concessions, and protesters’ vacating one of the government buildings they had occupied, belonging to the Ministry of Agriculture.

In Berlin, the German foreign minister, Frank-Walter Steinmeier, on Thursday called for Yanukovych and his allies to stop “playing for time.”

“Just finally get serious and do what you have promised the opposition,” Steinmeier said, addressing the Ukrainian authorities in an appearance before reporters and using a colloquial, familiar form of “you” not routinely associated with intergovernmental relations.

Germany has followed the drama in Ukraine closely, with 24-hour news channels reporting the latest developments and several media outlets and politicians hastening to Kiev.

Last week, Chancellor Angela Merkel said Germany was “outraged to the utmost” by Ukraine’s insistence on limiting freedom to demonstrate and by the use of violence against protesters.

On Wednesday, she opened a speech to Parliament with a renewed appeal to Ukrainians to stick to peaceful resolutions and demanded that the Ukrainian government not ignore the “many people who have shown in courageous demonstrations that they are not willing to turn away from Europe.”

“They must be heard,” she added, to applause.

There were signs in Kievlate Wednesday that negotiations were unraveling. The Party of Regions passed a version of an amnesty law for protesters that lacked support from opposition lawmakers. It stipulated that the amnesty would not take effect until the prosecutor general certified that protesters had vacated all occupied administrative buildings, including provincial capitols that were seized last week, and it set a 15-day deadline, requiring police action after that to clear the buildings.

Yanukovych was still at work Wednesday evening, attending a Party of Regions caucus meeting, although at least one report indicated that he was “pale” and said that he felt sick, adding credence to the report Thursday of his illness.

Attendees at the meeting said he had told lawmakers that, if they did not vote for the amnesty law, he would schedule a televised address to the nation, a phrase that some interpreted as a threat to declare a state of emergency.

Russia had said Wednesday that it was halting financial aid that has helped Ukraine avoid defaulting on its foreign debts, and would resume the aid only after a new government was formed. The Russian step was a signal of displeasure with the negotiations in Ukraine to resolve the crisis by bringing the pro-Western opposition into a coalition government to replace Azarov’s Cabinet, which was dismissed when he resigned.

The statement on the president’s website Thursday said that Yanukovych was “going on sick leave because of acute respiratory illness accompanied by a high temperature.”

There was no immediate reaction from the opposition politicians who had led the negotiations with Yanukovych.

Under the Ukrainian Constitution, if the president is incapacitated or dies, the prime minister serves as acting head of state. After Azarov resigned, Serhei Arbuzov became acting prime minister; both are allies of Yanukovych. There was no indication Thursday that Yanukovych intended to hand over authority to Arbuzov, even temporarily, because of the illness.

Front Section, Pages 6 on 01/31/2014