Trump will also host a bilateral meeting with the summit's co-host, Croatian President Grabar-Kitarovic.
During his trip to Poland, President Donald Trump gave a speech to a crowd in Krasinski Square praising the country's spirit, while addressing the need to "preserve our civilization" in the age of terrorism.
This comes as Mr Trump met with the Polish President ahead of the G20 Summit in Hamburg.
He called on all nations to confront North Korea's "very, very bad behavior", underscoring that Washington considered it a threat and saying the United States would "confront it very strongly".
He added: "So it was Russian Federation and it was probably others also, and that's probably been going on for a long period of time". "And they use it to blackmail us, to blackmail Ukraine", Lewicki said.
"The story of Poland is the story of a people who have never lost hope, who have never been broken, and who have never forgotten who they are", he said in his speech.
"We stand firmly behind Article 5", Trump said during a speech in Warsaw, Poland.
Mr Trump's critique of threats to the West did not appear to extend to Russia's actions past year during the presidential campaign.
The US President also reaffirmed his commitment to North Atlantic Treaty Organisation in his speech in Warsaw.
"Fake News is more important than North Korea's missile launch".
He started his day at the Royal Castle, welcomed by Mr Duda with a vigorous handshake in front of a white marble bust of Stanislaw August Poniatowski, the last king of Poland.
Macierewicz announced the decision on Thursday while Trump was on a state visit to Warsaw and meeting Polish top officials, among other things to discuss security and energy issues.
He argued variously that it could have been Russia, probably was Russia and indeed was Russia, while insisting it could have been other countries, too, adding: "I won't be specific". Every U.S. president since Harry Truman in 1949 has voiced the commitment that an attack on an alliance nation is an attack on all of them.
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