DONETSK, Ukraine — The pro-Russia insurgency in eastern Ukraine decided Thursday to go ahead with Sunday’s referendum on autonomy or even independence despite a call from Russian President Vladimir Putin to postpone it.

While Putin’s suggestion was seen as an effort to step back from confrontation and negotiate a deal with the West, he fueled tensions again on Thursday by overseeing military exercises that Russian news agencies said simulated a massive retaliatory nuclear strike in response to an enemy attack.

Putin said the exercise involving Russia’s nuclear forces had been planned back in November, but it came as relations between Russia and the West have plunged to their lowest point since the Cold War.

On the ground in Ukraine, many have feared that the referendum in the eastern regions of Donetsk and Luhansk could be a flashpoint for further violence between Ukrainian troops and the pro-Russia militants who have seized government buildings and police stations in about a dozen cities in the east. Ukraine launched a government offensive last week to try to oust the rebels and said at least 34 people were killed in the fighting.

The question on the ballot is: “Do you support the act of proclamation of independent sovereignty for the Donetsk People’s Republic?”

Despite the phrasing, organizers say only after the vote will they decide whether they want independence, greater autonomy within Ukraine or annexation by Russia.

The decision to hold the vote as planned was unanimous among rebel leaders, said Denis Pushilin, co-chairman of the so-called Donetsk People’s Republic.

He said Putin’s suggestion to postpone the vote “came from a person who indubitably cares for the population of the southeast” of Ukraine and thanked the Russian leader for his efforts to find a way out of Ukraine’s political crisis.