"We will accord special status to the Russian language and guarantee to protect it," Yatsenyuk said, adding that "major" constitutional reforms would also see a raft of powers handed to the regions.
Meanwhile, Russia on Friday said it was disappointed with the United States' assessment of an international deal to defuse the crisis in Ukraine, saying the threat of new sanctions against Moscow by Washington was "completely unacceptable".
The Foreign Ministry in a statement accused US officials of seeking to "whitewash" what it said was the use of force by Kiev's authorities against protesters in Ukraine's Russian-speaking eastern provinces.