WARSAW, Poland (AP) -- Most U.S. presidents use their foreign trips to promote the virtues of American democracy. President Donald Trump did some of that, too. But he didn't hesitate to use his quick visit to Poland to air some pointed grievances, blasting his predecessor, casting doubt on his own spy agencies and unloading on news outlets by name.

Trump's news conference with Polish President Andrzej Duda on Thursday offered a fresh window into how a new president, not yet six months in office, has shown a penchant for changing the unwritten rules of the White House.

Trump thumped former President Barack Obama for failing to do more to address allegations that Russia meddled in the 2016 election. At one point, Trump asserted that Obama had stayed silent because he expected his Democratic heir apparent to win.

"I think he thought Hillary Clinton was going to win the election, and he said, let's not do anything about it," Trump said. "Had he thought the other way he would have done something about it."

Trump was pressed about the conclusion by the U.S. national intelligence director last year that Russia was behind the hack of Democratic Party email systems and otherwise attempted to influence the 2016 election to aid Trump. Trump volunteered that U.S. spy agencies had once been confident that Iraq had weapons of mass destruction.

"They were wrong and it led to a mess," he said, meaning the Iraq war.

Russian President Vladimir Putin often makes the same argument about faulty U.S. intelligence when criticizing U.S. military action, most recently in response to Trump's decision to bomb a Syrian air base in retaliation for a chemical weapons attack blamed on the Syrian government. Russia disputed that finding.

All of it came on the eve of Trump's meeting with Putin and as investigators look into contacts between Trump's associates and Moscow during the 2016 campaign and transition.

Rep. Adam Schiff, D-Calif., the top Democrat on the House intelligence committee, said Trump's comments in Poland "continue to directly undermine U.S. interests. This is not putting America first, but continuing to propagate his own personal fiction at the country's expense."

While many U.S. presidents have pointed to a free and independent press as a pillar of democracy, Trump repeated his longstanding critique of CNN and singled out NBC News, complaining it was "equally as bad despite the fact that I made them a fortune with 'The Apprentice' but they forgot that." He was referring to the NBC reality show that introduced Trump to millions of Americans.

Trump appeared to find common ground with Duda, who complained about his treatment by a broadcaster. Last year, Duda signed a law designed to give his government more control of state media, drawing condemnation from watchdog groups.

"This is another example of Trump redefining the presidency," said Jeanne Zaino, political science professor at Iona College. "He is willing to say things past presidents would not say and break norms that his predecessors would not."

She added, "While this may upset some Americans, I imagine his supporters will cheer him on."

The exchanges brought to mind the principles espoused by Republican Sen. Arthur Vandenburg of Michigan, who called for an end to "partisan politics at the water's edge" following World War II and forged a bipartisan consensus for Democratic President Harry S. Truman's foreign policies.

Vandenburg's mantra has often been interpreted to mean that lawmakers should be discouraged from criticizing a sitting president while on foreign soil or while the president is abroad. But in recent years the maxim has not been honored like it once was. The atmosphere on foreign policy is more partisan.

Republican Mitt Romney criticized Obama during the president's 2012 trip to South Korea for making overtures to improve relations with Russia. Romney's criticism drew a stern rebuke from then House Speaker John Boehner, a fellow Republican, who said that "while the president is overseas, I think it's appropriate that people not be critical of him or our country."

A year ago, Obama didn't hold back on an Asia trip when he was asked what he thought of Trump, who had recently become the presumptive Republican nominee.

Obama said foreign leaders were "rattled by him" and said he believed that Trump had displayed "either ignorance of world affairs, or a cavalier attitude, or an interest in getting tweets and headlines" instead of doing what's required to "keep the world on an even keel."

Now Trump is president — and setting his own standard around the globe.

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EDITOR'S NOTE — Ken Thomas has covered the White House and national politics for The Associated Press since 2011.

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Associated Press writer Jonathan Lemire in New York contributed to this report.

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Follow Thomas on Twitter at https://twitter.com/KThomasDC