HAMBURG, Germany (CBSNewYork) -- President Donald Trump is in Hamburg, Germany, holding talks with numerous world leaders and getting ready for his much-anticipated meeting with Russian President Vladimir Putin at the G20 Summit.
Meanwhile, protesters clashed with police outside as the president met with German Chancellor Angela Merkel.
One key topic discussed was North Korea's nuclear program. In Warsaw, Trump spoke about the U.S. response.
"I don't like to talk about what I have planned," he said. "But I have some pretty severe things that we are thinking about."
The White House confirmed Trump will discuss Syria and ISIS during his first face-to-face meeting with Russian President Vladimir Putin on Friday.
Thursday morning, he delivered perhaps his strongest criticism of Russian activities since taking office.
"We urge Russia to cease its destabilizing activities in Ukraine and elsewhere and its support for hostile regimes, including Syrian and Iran," he said. "And to instead join the community of responsible nations in our fight against common enemies and in defense of civilization itself."
It's unlikely Trump will bring up Russian meddling in the election with Putin, though he did answer questions about possible Russian interference.
"I think it was Russia. But I think it was probably other people and/or countries, and I see nothing wrong with that statement," he said. "Nobody really knows. Nobody really knows for sure."
Trump also added criticism for President Barack Obama.
"He was told it was Russia by the CIA, as I understand it. It was well reported. And he did nothing about it. They say he choked," he said. "Well, I don't think he choked, I think what happened is he thought Hillary Clinton was going to win the election and he said let's not do anything about it. Had he thought the other way, he would have done something about it."
Senate Minority Leader Chuck Schumer (D-N.Y.) is among a group of Senate Democrats calling on the president to confront Putin about election meddling, saying failing to do so would be a "severe dereliction of duty."
Earlier Thursday, the president addressed the people of Poland, saying "the West will never, ever be broken."
Crowds waving flags cheered as Trump spoke in Krasinski Square, which is near the site of the Warsaw uprising against the Nazis in 1944.
"There is a courage and a strength deep in the Polish character that no one could destroy," he said. "The triumph of the Polish spirit over centuries of hardship gives us all hope in which good conquers evil and peace achieves victory over war."
Trump vowed to win the battle against extremism, saying "America and Europe have suffered one terror attack after another."
"We're going to get it to stop," he said. "I declare today for the world to hear the West will never, ever be broken, our values will prevail, our people will thrive and our civilization will triumph."
The president also stated that the U.S. stands "firmly behind Article 5,'' but repeated his call that NATO members "finally meet their full and fair financial obligation."
"Words are easy but actions are what matters," he said. "For its protection, everyone knows this, Europe must do more."
Trump added that America is "eager to expand our partnership" with Poland, saying "we welcome stronger ties of trade and commerce."
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