MOSCOW — Russian President Vladimir Putin is urging that a planned May 11 referendum on autonomy in southeast Ukraine be postponed.

In a meeting today with Swiss President Didier Burkhalter, Putin also called on Ukraine’s military to halt all operations against pro-Russia activists who have seized government buildings and police stations across at least a dozen towns in eastern Ukraine.

The Russian leader described Ukraine’s upcoming presidential election slated for May 25 as a move “in the right direction,” but repeated Russia’s long-held stance that constitutional reforms must precede any nationwide vote in Ukraine.

Roman Lyagin, chairman of the Donetsk People’s Republic election commission, said that Putin’s remarks notwithstanding, plans for holding an autonomy referendum on May 11 remained unchanged.

In Berlin, a leading Ukrainian presidential candidate said he was prepared to negotiate a decentralization of power as pro-Russia insurgents in the east have demanded.

But Petro Poroshenko, a billionaire chocolate magnate, added that some insurgents in the eastern region understand only “the language of force.”

The U.S. and European nations have increased diplomatic efforts ahead of Ukraine’s May 25 presidential election as a pro-Russian insurgency continues to rock the country’s eastern regions.