"We declare that we will guarantee the safety of international experts on the scene as soon as Kiev concludes a ceasefire agreement," the self-proclaimed Donetsk People's Republic's deputy premier Andrei Purgin said in a statement.
He urged Kiev to "immediately conclude such an agreement" with the rebels.
Failure to do so would give the impression that the government is made up of "dangerous lunatics, bloodthirsty maniacs (who are) dangerous not only for the residents of Donbass but also for the world community", Purgin warned.