According to Bloomberg News sources who claim to have attended his closed-door speech, Russian President Vladimir Putin told his diplomats that he made an offer to resolve the conflict in eastern Ukraine during his summit with President Donald Trump in Helsinki on Monday.

Bloomberg reports Putin gave this account of the meeting to a conference of Russian ambassadors and other officials at the Foreign Ministry in Moscow on Thursday. According to one source, the meeting was kept private because Trump asked Putin to give him some time to consider the offer.

Putin’s offer to Trump was purportedly to call a referendum overseen by international observers and allow separatist Ukraine territories to vote on their status. The referendum would be modeled on the one held in Crimea in 2014, which Russia claims ratified its annexation of Crimea as justified and supported by the residents.

The Crimean referendum was not monitored by international observers, and Russia has a history of demanding respect for votes regarded as sketchy or downright illegal by the United States and Europe.

For their part, the Ukrainian government said on Wednesday that it regards Putin’s endorsement of the Crimean referendum as tantamount to the Russian leader confessing to a crime. Ukrainian President Petro Poroshenko dismissed the Crimean referendum as “ridiculous” because the rolls were packed with Russians.

The Hill anticipates the U.S., Ukraine, and European Union will regard any proposal for a referendum on the separatist regions as a violation of the 2015 Minsk agreement, in which Russia made a commitment to respect the political and territorial integrity of Ukraine.