Ukrainian officials on May 28 said Russia should put forth its peace plan for ending the war in Ukraine immediately instead of waiting for a new round of talks next week in Istanbul.

Russia said it wants the talks with Ukraine to take place on June 2 and will use the meeting to present a "memorandum" outlining its terms for a peace settlement.

"Our delegation, led by Vladimir Medinsky, is ready to present a memorandum to the Ukrainian delegation and provide the necessary explanations during a second round of direct talks in Istanbul on Monday, June 2," Russian Foreign Minister Sergei Lavrovsaid in a statement.

Lavrov said the memorandum will set out Russia's views "on all aspects of reliably overcoming the root causes of the crisis."

Medinsky, a Russian political scientist and former culture minister, led Russia's negotiating team on May 16 during the first round of direct talks in the more than three years since Russia launched its full-scale invasion of Ukraine.

US Secretary of State Marco Rubio spoke with Lavrov and welcomed a prisoner exchange over the weekend, spokeswoman Tammy Bruce said in astatement.

"The Secretary reiterated President Trumps calls for constructive, good faith dialogue with Ukraine as the only path to ending this war," Bruce said.

Putin'sdemands for ending the warinclude a written pledge from Western leaders that NATO will not expand to former Soviet republics such as Ukraine and Georgia and the lifting of some sanctions on Russia, according to Russian sources with knowledge of the negotiations quoted by Reuters.

The Kremlin has previously demanded Ukraine cede territory that Russia already controls -- a proposition Ukraine has called unacceptable.

The round of talks on May 16 yielded no breakthrough but was followed by a large prisoner exchange, and the two sides agreed to work on respective peace proposals.