KYIV, March 25 (Reuters) - The U.S. is making its offer of security guarantees for a peace deal in Ukraine conditional on Kyiv ceding all of the country's eastern region of ‌Donbas to Russia, President Volodymyr Zelenskiy told Reuters in an interview. With the U.S. focused on its own conflict with Iran, President Donald Trump is applying pressure to Ukraine in an effort to bring a quick end to the four-year war triggered by Russia's 2022 invasion, Zelenskiy said.