WARSAW, Poland (AP) - President Donald Trump says he agrees that Russia meddled in the 2016 presidential election, but he is repeating his assertion that he believes "other countries" may have done the same.

Trump did not elaborate on which other countries he believes meddled in the 2016 election during his remarks in Warsaw, Poland Thursday. He says "nobody really knows for sure."

He was speaking a day ahead of his first face-to-face meeting with Russian President Vladimir Putin.

Trump also repeated his claims that former President Barack Obama knew that Russia was meddling in the election.

Trump said people say Obama "choked" but he believes Obama purposely "did nothing" because he thought Democrat Hillary Clinton would win the election.

Also during his press conference with the Polish president Thursday, President Trump called on nations to confront North Korea's "very, very bad behavior."

The president says he's considering some "very severe things" to respond to North Korea's test launch of an intercontinental ballistic missile. But he adds that that doesn't mean he's going to follow through on them.

Trump says he wants to look at what happens over the coming weeks and months and calls North Korea's behavior "a shame."

Trump says the North is behaving in a "very, very dangerous manner" and that something will have to be done about it.

North Korea launched the missile earlier this week. The issue will be a topic of discussion when Trump meets with world leaders in Germany later this week.