DONETSK, Ukraine -- Ukraine's prime minister went on a charm offensive Friday as he visited the country's southeast, pledging to give regions more powers and to defend the rights of Russian speakers.

Arseniy Yatsenyuk met with regional officials who once opposed his new government in Kyiv, but not with protesters occupying government buildings in the cities of Donetsk or Luhansk. Still, he left it unclear how his ideas differed from the demands of the protesters or from Russia's advocacy of federalization for Ukraine.

"There are no separatists among us," said Gennady Kernes, mayor of Kharkiv, Ukraine's second-largest city, where the government recaptured a building taken over by protesters earlier in the week. Kernes and other officials asked Yatsenyuk to allow votes on autonomy for their regions but not on secession.

Ukraine's government has resisted federalization, saying that would lay the groundwork for the country's breakup.

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 -- but only after Russia took over the peninsula by force.

Russia has ratcheted up the pressure on Ukraine, with President Vladimir Putin warning European leaders of a risk to the gas supplies going to them through Ukraine. He has threatened that Russia could shut off energy shipments to Ukraine if it fails to pay its debts. Those debts are a source of contention between the two nations, with the Russian estimate rising from $1.7 billion earlier this month to over $35 billion on Thursday.

Before leaving Donetsk for another eastern city, Yatsenyuk told reporters he favours a peaceful solution to the standoff. However, he left the door open to storming the buildings occupied by armed men.

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 a vote on autonomy, with the possibility of holding another later on whether to join Russia.

Eastern Ukraine has a high proportion of Russian-speakers and many of them fear being repressed by the acting government in Kyiv that took over when Yanukovych fled

Yatsenyuk sought to assuage these fears in a live TV interview.

"I will be the first to guarantee the right of every Ukrainian to speak any language they want," he said, speaking in Russian. "I have never met any Russian-speaking Ukrainian who would say he wants protection because he is not allowed to speak Russian."

Kyiv and Western officials say Russia is whipping up tensions in eastern Ukraine to establish a pretext for sending in troops.

Russian Foreign Minister Sergey Lavrov, however, denied any participation by Russia in the events in the east, saying Friday on Rossiya television 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 dismissed earlier calls by the protesters for Russia to send in peacekeeping forces.

"We want Ukraine to be whole with its current borders," Lavrov said.

NATO Secretary General Anders Fogh Rasmussen, visiting Bulgaria on Friday, again urged Russia to pull back its troops from Ukraine's borders. NATO estimates those troops to be up to 40,000 forces.

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, Bulgaria, Russia and Ukraine all border the Black Sea.

Alexander Roslyakov in Donetsk, Nataliya Vasilyeva in Kyiv, 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.