ISTANBUL

US President Donald Trump said Sunday that he is "very disappointed" over Russia's ongoing missile strikes against Ukraine amid peace negotiations.

"I was very disappointed that missiles were flying by Russia...very disappointed," Trump told reporters before boarding Air Force One at Morristown Municipal Airport in Morristown, New Jersey, saying he is "surprised" by the continued bombardment during the talks.

Asked what he expects from Russian President Vladimir Putin, he responded: "Well, I want him to stop shooting, sit down and sign a deal. We have the confines of a deal, I believe, and I want him to sign it and be done with it and just go back to life.”

When a reporter asked: “Do you trust President Putin?” Trump responded: “I’ll let you know in about two weeks,” without elaborating.

Trump also discussed his meeting with Ukrainian President Volodymyr Zelenskyy at the Vatican on the sidelines of Pope Francis’s funeral, their first face-to-face encounter since a heated White House meeting in February.

"I think the meeting went well. We'll see what happens over the next few days," he said, adding his relationship with the Ukrainian leader "was never bad."

Trump characterized Zelenskyy as "calmer" during their Vatican discussion.

"I think he understands the picture, and I think he wants to make a deal. I don't know if he wanted to make a deal (before)," he said.

Regarding nuclear talks with Iran, Trump expressed optimism.

"The Iran situation, I think we're doing very well. I think a deal is going to be made there...We'll have something without having to start dropping bombs all over the place."

Trump has threatened military action against Iran if a new agreement is not reached to replace the 2015 nuclear deal brokered during the Barack Obama administration.

He has repeatedly emphasized that Iran "cannot have a nuclear weapon."