The Kremlin denied on Monday any knowledge of a peace plan for Ukraine put forward by a Ukrainian lawmaker and two associates of President Trump.

The proposal, reported by The New York Times on Sunday, would essentially require the withdrawal of all Russian forces from eastern Ukraine and would allow for Ukrainian voters to decide in a referendum if Crimea, the Ukrainian territory seized by Russia in 2014, would be leased to Russia for 50 or 100 years. It also outlined a way for the Trump administration to lift sanctions against Russia.

The plan was put forward, The Times reported, by Michael D. Cohen, the president’s personal lawyer, who said he had delivered the document to the White House; Felix H. Sater, a business associate who has helped Mr. Trump scout deals in Russia; and a Ukrainian opposition lawmaker, Andrii V. Artemenko, trying to rise in a political opposition movement shaped in part by Mr. Trump’s former campaign manager Paul Manafort.

While there is nothing illegal about unofficial diplomatic efforts, the revelations of the proposal, which seemed to advance Russian interests, come as the Trump administration is under intense scrutiny over any ties to Russia. Mr. Trump’s national security adviser, Michael T. Flynn, resigned last week — ending the shortest tenure of anyone in that position since it was created in 1953 — over concerns that he had misrepresented his communications with the Russian ambassador to Vice President Mike Pence.