In February 2017, Donald Trump’s personal attorney Michael Cohen hand-delivered to Michael Flynn a document describing a proposed “peace plan” between Russia and Ukraine. The plan involved the US dropping all sanctions on Russia; holding a Ukrainian referendum on whether to lease Crimea to Russia for 50–100 years; and disseminating “kompromat” on Ukrainian President Poroshenko purportedly showing corruption among him and his closest associates, with the goal of installing a more Russia-friendly government in Ukraine.
The plan was prepared by Andrii Artemenko, a Ukrainian lawmaker who joined their Parliament in 2014 and opposed their new President Poroshenko. Artemenko indicated that top aides to Vladimir Putin had provided input.
Artemenko got the plan to Cohen via Felix Sater, a Russian-American businessman formerly with Bayrock Group (located in Trump Tower and with whom Trump had done business before), who had previously pleaded guilty for his role in a stock manipulation scheme that involved the Russian Mafia. Source