Trump: President Zelensky 'not easy to work with'

Mr. Trump, who has repeatedly said he finds it easier to work with Moscow than Kiev in efforts to broker peace between the two countries, reiterated a similar view on May 19 when asked whether he believed Ukraine was “doing enough” to end the conflict.

"I want to tell you in about two weeks, because I can't say 'Yes' or 'No'... Look, Mr. Zelensky is a strong person, and he's not the easiest person to work with. But I think he wants to stop... I hope the answer is he wants to solve this problem," Mr. Trump told reporters at the White House, after separate phone calls with President Putin and President Zelensky earlier in the day.

Last week, Mr. Trump said “nothing will happen until Putin and I meet,” and urged Kiev to “immediately” accept Moscow’s proposal for direct talks. Asked if he still held that view after the Istanbul talks and the latest calls, Mr. Trump said he remained cautiously optimistic.

"I tell you, there are big egos involved, but I think something will happen. And if it doesn't, I'll pull out and they'll have to move on," Mr. Trump said, but declined to explain what might prompt him to abandon the reconciliation effort.

“I have a certain limit, but I don't want to say what it is because I think it makes the negotiation more difficult,” he added.

Mr Trump said the call with President Putin "went very well" and "progress is being made", but gave few details about the follow-up call with Mr Zelensky.

The US president has long suggested that Kiev is more difficult to work with, recalling a tense Oval Office meeting in February where the Ukrainian delegation reportedly left early and only returned when Mr Zelensky was “ready for peace”.

On the Ukrainian side, President Zelensky said he spoke to Mr. Trump twice on May 19 – before and after the US President's call with Mr. Putin – and warned Mr. Trump not to make any decisions about Ukraine without Kiev's participation.

Despite insisting Ukraine wants to "end the war", Mr Zelensky said Kiev would not agree to any Russian "ultimatums" and once again demanded nothing less than a "complete and unconditional ceasefire".

Meanwhile, President Putin described the two-hour call with Mr. Trump as "frank" and "quite useful," and announced that Moscow was ready to work with Kiev on a tentative memorandum for a future peace deal.

"In general, Russia's position is clear. The main thing for us is to eliminate the root causes of this crisis," Mr. Putin said.