And Arseniy Yatsenyuk -- an opposition leader from a party other than Klitschko's -- made a public appeal to Yanukovych: "Do not let Ukraine become a country covered with blood. Pull back the police and announce a cease-fire. Then we will negotiate."
U.S. Vice President Joe Biden himself pressed Yanukovych in a phone call, with the White House saying "the government bears special responsibility to de-escalate the situation."
Secretary of State John Kerry later backed up the Vice President's words. He called for the Ukrainian government to halt violence immediately, and reopen dialogue with the opposition.
On the flip side, Russia's state-run RIA Novosti's story on the latest Kiev unrest noted Moscow's persistent support for Yanukovych and its accusation -- made earlier this week from foreign ministry spokesman Alexander Lukashevich -- that Washington is trying to tell "the authorities of a sovereign state what they should do next and how they should do it."
Such international back-and-forth is especially significant in the Ukraine, given not only its geographic and political position betwixt Europe and Russia and the origins of the latest unrest.
It began in November with Yanukovych's decision to scuttle an European Union trade pact that the opposition hoped would bring the Ukraine closer to the West, and improve its economy in the process.
The next month, Russian President Vladimir Putin announced that Russia would buy $15 billion in Ukrainian debt and slash the price Kiev pays for its gas.
As the months rolled on, the conflict expanded beyond the long-simmering discord over whether Ukraine should align more with the West or with Russia.
The opposition has pressed to change how the Eastern European nation's government operates, namely through constitutional and other reforms that would -- among other things -- shift powers away from its president and toward parliament.