U.S. President Donald Trump said in Warsaw on July 6 that the United States is "committed to maintaining peace and security in Central Europe," and is "working with Poland in response to Russia's actions and destabilizing behavior."

Speaking after meeting with Polish President Andrzej Duda, Trump also reaffirmed Washington's commitment to the NATO alliance, saying: "Our strong alliance with NATO and Poland remains critical to deterring conflict and ensuring that war between great powers never again ravages Europe and that the world will be a safer and better place."

Poland’s proximity to Russia has heightened its concerns about Moscow’s intentions in the region, especially after Russia’s illegal annexation of Ukraine’s Crimea region, its support of separatists in eastern Ukraine, and its alleged public opinion manipulation campaigns during elections in the United States and some European Union countries.

Standing alongside Duda at a joint press conference after their July 6 meeting, Trump told reporters he thinks Russia meddled in the 2016 U.S. presidential election, but said "nobody really knows for sure."

"I think it was Russia and I think it could have been other people in other countries," he said without elaborating.

Trump's remarks came shortly before he was scheduled to meet leaders of Central and Eastern European states and make a televised speech to the people of Poland.

Later on July 6, Trump was due to travel to Hamburg, Germany for the Group of 20 (G20) summit. He plans to meet on July 7 with Russian President Vladimir Putin on the sidelines of the G20 summit.

In Warsaw, he was to speak to heads of state and government at the Three Seas Initiative Summit in Warsaw (eds. 11:10 a.m. Prague time) -- a joint project of Poland and Croatia that was launched in 2016 with the aim of strengthening trade, infrastructure, and cooperation on energy and politics between countries that border the Adriatic Sea, the Baltic Sea, and the Black Sea.

Other countries involved in the initiative include Hungary, the Czech Republic, Slovakia, Romania, Bulgaria, Lithuania, Estonia, Latvia, Slovenia, and Austria.

The White House said Trump would encourage leaders at the summit who are wary about their dependence on Russian energy to take advantage of newly available supplies of U.S. natural gas.

Trump’s keynote speech in the Polish capital is scheduled in the early afternoon, a televised address given at Warsaw’s Krasinski Square.

Poland’s populist leaders have expressed support for Trump’s policies and his view of the world, from anti-immigrant themes to an apparent weakening of support for international organizations.

Poland’s ruling Law and Justice party (PiS) has promised to bus in pro-government activists to hear Trump’s televised address.

Still, Polish leaders – like many others across Europe -- were anxious to hear the U.S. president renew his country’s commitment to NATO and to the alliance’s Article 5, the provision that states an attack on one NATO country is an attack on all members of the alliance.

In his first trip to Europe in May, Trump shocked many NATO members when he failed to mention Article 5 and instead berated allies for a lack of spending on their defense, claiming the United States shouldered an unfair burden of the costs.

H.R. McMaster, Trump's national security adviser, told reporters last week that Trump will use his Warsaw speech to reiterate the U.S. commitment to the western alliance.

"He will lay out a vision not only for America's future relationship with Europe, but the future of our transatlantic alliance, and what that means for American security and American prosperity," McMaster said.

Immediately after that speech, the U.S. president plans to leave Poland for the G20 summit in Hamburg.

Trump and Putin were scheduled to meet for the first time on July 7 on the sidelines of the G20 summit.

The Syrian conflict was expected to be high on the agenda – including a U.S. proposal to cooperate on creating no-fly zones in Syria.

Trump also will hold one-on-one talks with British Prime Minister Theresa May in Hamburg on July 7, May's office announced.

Some 20,000 police have been deployed in Hamburg to provide security during the G20 summit.

Hamburg police clashed with demonstrators on the night of July 5 ahead of the meetings, using water cannons to disperse some protesters. Germany has said that among tens of thousands of protesters expected to converge on Hamburg during the summit, as many as 8,000 could potentially be involved in rioting and other violence.

Trump was expected to face tough questions at the G20 gathering from European leaders over his decision to pull the United States out of the Paris climate accord. He also faces skepticism about his perceived lack of support for NATO and the European Union, and his commitment to Ukraine’s sovereignty in the backdrop of his desire to improve relations with Russia and his praise for Putin personally.

Tough talks on free-trade issues and immigration were also expected.
Western allies will also expect Trump to push Putin on Russia’s interference in eastern Ukraine, which has led to a war that has killed more than 10,000 people.

Trump will also look to push Russia -- and, more importantly perhaps, China -- to put more pressure on North Korea to halt its nuclear and ballistic-missile programs.

Trump has expressed disappointment that China has not done in more to rein in its North Korean ally, which on July 4 tested its first intercontinental ballistic missile.

Trump’s interactions with German Chancellor Angela Merkel also will be closely watched. The two have, so far, had what were perceived as awkward moments during talks in Washington and during Trump’s first trip to Europe in May.

Merkel has spoken in recent days about “obvious” disagreements with Washington and her ruling Christian Democratic Union (CDU) recently dropped the term “friend” to describe Germany’s relationship with the United States.

With reporting by AP, Reuters, dpa, CNN, CNBC, and The Wall Street Journal