Ukraine's ambassador to the United States said Monday he's worried Donald Trump "doesn't have all the facts" about Russia's activities and intentions in Ukraine.

In an interview on CNN, Valeriy Chaly said he met with the Trump campaign in Cleveland during the GOP convention, and was assured the Republicans did not accept Russia's claim to Crimea.

But now, in light of an interview Trump gave to ABC's "This Week" he says he's not sure of Trump's position.

"I met with Mr. Trump's team and everybody told me, 'everything's okay, we keep this position we reject any annexation of your territory in Crimea from Russian side,' But now I am certainly concerned by the change of this position by the candidate," Chaly told CNN.

On Sunday, Trump told ABC's George Stephanopoulos that he was not involved in a rewriting of the GOP party platform to eliminate a call for providing lethal weapons to Ukraine to defend themselves, and insisted Russian President Vladimir Putin was "not going into Ukraine."

"Just so you understand," Trump said. "He's not going to go into Ukraine, all right? You can mark it down and you can put it down, you can take it anywhere you want."

When Stephanopoulos replied "Well, he's already there, isn't he?" Trump quickly backtracked, saying "OK, well, he's there in a certain way, but I'm not there yet."

Trump sent a couple of tweets on Monday clarifying his position. "When I said in an interview that Putin is 'not going into Ukraine, you can mark it down,' I am saying if I am President. Already in Crimea!" Trump tweeted. "So with all of the Obama tough talk on Russia and the Ukraine, they have already taken Crimea and continue to push. That's what I said!"

Ambassador Chaly said he was still confused. "I do not want to be involved in the election," he said. "It is the American people who will decide who will be president of the United States, but we count on the United States having a predictable leadership and predictable foreign policy. So that's the main push from our side."