US President Donald Trump is to argue that the future of Western civilisation is at stake in a keynote speech in the Polish capital Warsaw.
Holding up Poland as an example of a country ready to defend civilisation, he will warn against the threats of "terrorism and extremism".
Poland's conservative government shares Mr Trump's hostile view of immigration and strong sense of sovereignty.
Mr Trump is in Poland ahead of a G20 summit in Hamburg, Germany.
"Because as the Polish experience reminds us - the defence of the West ultimately rests not only on means but also on the will of its people to prevail," Mr Trump will say, according to excerpts released from the speech.
"The fundamental question of our time is whether the West has the will to survive."
Security in Hamburg has been tightened, with 10,000 people expected to gather for protests during the day and police warning of potentially violent clashes. They have already confiscated a number of homemade weapons.
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In the speech at the monument to the 1944 Warsaw Uprising on Krasinski Square, Mr Trump will also reaffirm US support for Eastern Europe ahead of his first meeting with Russian President Vladimir Putin at the G20 summit in Hamburg, the BBC's James Landale in Warsaw reports.
Mr Putin called for an end to sanctions against Russia as well as trade protectionism in an editorial published in German newspaper Handelsblatt.
The big question will be how strongly Mr Trump will emphasise America's commitment to Nato's mutual defence, our correspondent says.
Mr Trump once described Nato as an "obsolete" alliance, criticising other members for not spending more on defence.
Nato and Trump: What future for Atlantic alliance?
American gas for Europe?
Mr Trump's day began with the Three Seas summit - a Polish and Croatian initiative bringing together 12 nations between the Baltic, the Adriatic and the Black Sea.
Mr Trump was expected to bang the drum for US trade, telling the gathering that US gas imports could reduce their reliance on Russia.