President Donald Trump on Thursday set the tone for his upcoming meeting with Russian President Vladimir Putin, using his most direct rhetoric yet toward Moscow when he urged the Kremlin to “cease its destabilizing activities.”

When Trump and Putin hold a formal meeting Friday during the G-20 summit in Hamburg, Germany, it will be one of the most anticipated meetings between an American and a Russian leader in some time. The U.S. president used a Thursday speech to the Polish people in Warsaw to set the tone, making clear he wants Putin to alter course while stating clearly his commitment to NATO’s mutual defense pact, established in large part to deter Soviet, and later Russian, aggression.

Observers of all political and ideological stripes are watching closely to see if Trump will forcefully warn Putin against any future efforts to meddle in American elections, as well as just how hamstrung the U.S. leader is in seeking the closer ties with Moscow he craves due to an ongoing scandal over potential nefarious ties between his presidential campaign and Russian officials.

In his Warsaw address, Trump urged Russia “to cease its destabilizing activities in Ukraine and elsewhere,” and also called on Moscow to end its support for what he dubbed the “hostile regimes” in Syria and Iran.

Instead, Russia should “join the community of responsible nations” in its battle “against common enemies” and in pursuit of the “defense of civilization itself,” he said.

And while Trump initially acknowledged that Russia had likely meddled in U.S. elections in a news conference before his speech, he later backed away from that and gave the Kremlin some wiggle room, saying, “I think it was Russia. I think it was other countries, as well. No one really knows.”

Trump’s tougher-on-Russia remarks came in front of a crowd composed of officials from and supporters of the conservative ruling party in Poland. But since Trump often alters his stances — and seems influenced by his audience — there is a chance he would be less critical during his meeting with Putin.

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Trump has drawn criticism at home and across Europe for what lawmakers and longtime foreign policy experts have called his lukewarm belief in Article 5 of the NATO charter. “Collective defence means that an attack against one ally is considered as an attack against all allies,” reads a summary of the provision and its intent posted on the alliance’s website.

“We firmly stand behind Article 5, the mutual defense commitment,” Trump said Thursday, a remark that was perhaps his most definitive pledge to adhere to the provision since taking office.

But, in his signature fashion, the American commander in chief also noted he has “demanded” that all NATO members increase how much they devote to the alliance’s coffers each year. And he repeated his assertion that “billions” more in funds from NATO members are “pouring in” than before he was sworn in on Jan. 20. (An uptick in member funding began under the Obama administration, according to military analysts.)

Despite that line critical of America’s NATO allies, Trump vowed to defend them in the face of what he described as threats — “whether they come from inside or out, from the south or the east, that threaten over time to undermine these values and to erase the bonds of culture, faith and tradition that make us who we are.”

Southern-approaching threats were a reference to extremist groups such as the Islamic State, which has claimed responsibility for a string of attacks across Europe. The eastern threats appeared a veiled reference to Russia.

To that end, Trump, in several parts of a speech penned largely by senior adviser Stephen Miller, referenced the many times Poland has been invaded and occupied by other countries, including the former Soviet Union.

During four decades of “Communist rule,” Soviet officials waged an effort to “destroy” Poland’s “culture” and “humanity,” Trump said.

“Your oppressors tried to break you,” he said to a crowd that repeatedly chanted his name, “but Poland could not be broken.”

And in one of several messages to Putin, Trump touted a coming sale of the U.S.-made Patriot missile defense systems to Poland. The two countries finalized an agreement to that end on Wednesday evening.

Putin and other Russian officials often publicly state that such deployments are a threat to Russian sovereignty despite U.S. and European leaders’ contentions that they are purely defensive and not solely meant to counter possible Russian missile launches.

Though Russia’s support for Syria and Iran and the missile sale will garner ample attention, Trump also used an expected U.S.-Poland natural gas pact to send a message to Putin several times on Thursday.

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“The United States will never use energy to coerce your nations,” Trump told the leaders of the dozen countries located between the Baltic, Black and Adriatic seas. It was his second veiled jab at Russia of the day — even as he gave Moscow some cover over meddling in the U.S. election.

During a joint news conference earlier in the day, Polish President Andrzej Duda predicted the governments soon will finalize an agreement that will give the “green light” to a long-term contract that will allow more American natural gas to be exported to Poland. Duda even went so far as to say he sees his country becoming a “hub” for U.S. gas to flow to other European countries.

In a section of what White House officials had dubbed a “major speech” that will likely be welcomed in Moscow, Trump appeared to criticize the European Union.

He lambasted a “steady creep of government bureaucracy that drains the vitality and wealth of the people,” saying “the West became great not because of paperwork and regulations, but because people were allowed to chase their dreams and pursue their destinies.”

“Americans, Poles, and the nations of Europe value individual freedom and sovereignty,” Trump, the proponent of the British people’s decision to leave the EU, said on European soil.

However, the American president’s address carried an undercurrent of a dark gloominess as he questioned whether Western civilization is doomed to crumble.

“As the Polish experience reminds us: The defense of the West ultimately rests not only on means but also on the will of its people to prevail,” Trump said. “The fundamental question of our time is whether the West has the will to survive.”

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The U.S. president essentially delivered this message: The West’s survival is being tested by forces such as violent Islamic extremist groups, Russia and globalist groups like the EU. By applauding the Polish “spirit” and grit to remain an independent country, Trump appeared to be using it as an example of how his “America First” philosophy will work back home.

Part of that “America First” philosophy is a tough stance on immigration. To that end, Trump said this: “While we will always welcome new citizens who share our values and love our people, our borders will always be closed to terrorism and extremism.”

Though his speech was chock full of references to Polish occupation and defeats, warnings about common threats, and a warning that the West could fall, the president ended on a high note.

“The West will never, ever be broken,” he said. “Our civilization will triumph.”

Foreign policy experts reacted to the speech with a mixture of tepid optimism and criticism, with Nicholas Burns, a former undersecretary of state for political affairs, tweeting that Trump did little to help his German and French counterparts.

Trump uses Warsaw speech to criticize European Union. Plays to right wing Polish government. But won’t help with Merkel and Macron.

— Nicholas Burns (@RNicholasBurns) July 6, 2017

Welcome criticism of Russia over Ukraine & reaffirmation of NATO Article 5 in otherwise tired & tedious speech by Potus in Poland.

— Richard N. Haass (@RichardHaass) July 6, 2017