During a phone call in June, Biden was testy when Zelensky began listing what else Kyiv needed and didn’t get shortly after the US president announced the aid package, NBC News reported. The commander-in-chief is said to have briefly lost his temper and reminded Zelensky that “the American people have been generous enough” and stressed that the White House and the US military were doing everything they could to help Ukraine in its war with Russia. The president’s frustration was said to have been building for weeks before the June 15 phone call, with Biden confiding in aides that he believed his administration was pulling out all the stops to help his ally, but that Zelenskiy continued to focus on what was not possible. A spokesman for the National Security Council declined to comment for the NBC story. A spokesman for Mr. Zelensky’s office also did not respond to a request for comment.

“The relationship has since improved”

The news agency’s sources said the presidents’ relationship has improved since the tense exchange, with the White House poised to ask Congress for tens of billions more in Ukraine aid in the new year. Speaking about the announcement at the time, Lloyd Austin, the US defense secretary, said the US and Ukraine were “working tirelessly to meet Ukraine’s requests for new capabilities”. The batch included 18 shells, 36,000 rounds of ammunition and two Harpoon coastal defense systems.