New Delhi, May 15 -- US President Donald Trump on May 15 cast doubt over any progress in Ukraine-Russia peace talks, stating that negotiations will only move forward when he meets face-to-face with Russian President Vladimir Putin.

Speaking to reporters aboard Air Force One en route to Dubai, Trump said, "Nothing's going to happen until Putin and I get together."

He added that Putin had opted out of the scheduled Istanbul summit because he believed Trump would also be present.

"He was going to go, but he thought I was going to go. He wasn't going if I wasn't there," Trump explained.

"I don't believe anything's going to happen, whether you like it or not, until he and I get together. But we're going to have to get it solved, because to...