WASHINGTON — President Trump on Friday released a memorandum of an April telephone conversation he had with President Volodymyr Zelensky of Ukraine that differed from a summary of the call released by the White House months ago.

The memorandum of the call, which took place after Mr. Zelensky won a landslide presidential election, shows the two men praising each other’s political acumen and predicting an era of warm relations between the United States and Ukraine. There is no mention of Mr. Trump’s determination to have Ukraine’s government investigate his political rivals — one subject of a July phone call that has become the focus of an impeachment inquiry in Congress.

But a White House readout of the call in April offers a different account. In that summary, provided to reporters shortly after the call took place, the administration said that Mr. Trump promised to work with Mr. Zelensky “to implement reforms that strengthen democracy, increase prosperity and root out corruption.”

A White House spokesman, Hogan Gidley, gave no explanation for the discrepancy but said “it is standard operating procedure for the National Security Council to provide readouts of the president’s phone calls with foreign leaders. This one was prepared by the N.S.C.’s Ukraine expert,” an apparent reference to Lt. Col Alexander Vindman, who has given damaging testimony about Mr. Trump in a closed-door deposition and is scheduled to testify in public next week.