The officials who met Arseniy Yatsenyuk in Donetsk did not include representatives of the protesters. The officials asked Yatsenyuk to allow referenda on autonomy for their regions, but not on secession.
"There are no separatists among us," said Gennady Kernes, mayor of Kharkiv, Ukraine's second-largest city, where protesters had occupied a government building earlier in the week.
Ukraine's eastern industrial heartland was the support base for Kremlin-friendly president Viktor Yanukovych, who was ousted in February after months of protests. Last month, the Crimea region voted to secede and was annexed by Russia.
Russia ratcheted up the pressure on Ukraine on Thursday when President Vladimir Putin warned European leaders of a risk to the gas supplies going through Ukraine. He has threatened that Russia could shut off shipments to Ukraine if it fails to pay its mammoth debts.
Putin's spokesman Dmitry Peskov told Russian news agencies on Friday that Russia has not heard from the countries to which Putin sent a letter.
Protesters in the eastern cities of Donetsk and Luhansk are occupying government buildings and calling for referenda on regional autonomy that could prefigure seeking annexation by Russia.
Before leaving Donetsk for another eastern city, Yatsenyuk told reporters that he favors a peaceful solution to the stand-off. However, he left the door open to storming the buildings occupied by armed men, though a two-day deadline announced earlier this week has passed.
Yatsenyuk said the grievances of eastern Ukraine would be appeased by the upcoming constitutional reform that will "satisfy people who want to see more powers given to regions." He mentioned abolishing Kiev-controlled local administration as one of the steps to decentralize the country.
The protesters in Donetsk, who have held the regional administration building since Sunday, initially called for a referendum on secession but later reduced the demand to one on autonomy, with the possibility of holding another later on whether the region would remain part of Ukraine or seek to become an autonomous region within Russia.
The eastern parts of Ukraine have a high proportion of Russian-speakers and many of them fear that the acting government that took over when Yanukovych fled will repress them. Kiev and Western officials, in turn, claim that Russia is whipping up tensions in the east, with the aim of establishing a pretext for sending in troops. Russian Foreign Minister Sergey Lavrov denied any participation by Russia in the events in the east, saying on Rossiya television on Friday that "our servicemen aren't there. Our agents aren't there."
He also said Russia does not aim to annex any parts of eastern Ukraine and "we want Ukraine to be whole with its current borders." He also dismissed earlier calls by the eastern Ukraine protesters for Russia to send in peacekeeping forces.
Russia is calling on Ukraine to change its constitution to become a federalized state in which regions would have more control of their own affairs. Ukraine's government has resisted federalization, saying that would lay the groundwork for the country's breakup.
NATO Secretary General Anders Fogh Rasmussen who was visiting Bulgaria on Friday again urged Russia to pull back its troops from Ukraine's borders, and added that NATO is taking legitimate steps to deal with the instability created by Russia's "illegitimate" actions.
Speaking in Prague, Czech President Milos Zeman called on NATO and the European Union to take robust pre-emptive actions to deter Russia from invading other parts of Ukraine after its takeover of Crimea. He stopped short of giving details.
In northwest Romania, some 450 U.S. and Romanian troops were conducting joint military exercises, flying U.S. F-16 fighter jets alongside Romanian ones. Romania, Russia and Ukraine all border the Black Sea.
In a bid to apply pressure on Russia, the European Union has warned Moscow of further sanctions for ratcheting up tensions in Ukraine.
A senior European Union official who spoke on the condition of anonymity said the 28-nation bloc's foreign ministers would consider broadening the list of people sanctioned to deter Russia from further destabilizing the situation in eastern Ukraine.
The person, who was briefing reporters on condition of anonymity, said ministers at Monday's meeting in Luxembourg aren't expected to decide new sanctions but could agree on ordering the preparation of a new list of targets.
Russia's Lavrov on Friday blamed the crisis on the West and its support for Ukraine's fledging government which he described as illegitimate. Lavrov said the solution to the crisis would be a "deep" constitutional reform in Ukraine that would guarantee Ukraine's "nonaligned status," meaning a guarantee that it would not join NATO.
Alexander Roslyakov in Donetsk, Nataliya Vasilyeva in Kiev, Ukraine, Jim Heintz in Moscow, Juergen Baetz in Brussels, Karel Janicek, in Prague, Czech Republic, and Veselin Toshkov in Sofia, Bulgaria, contributed to this story.
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