New York, New York - Prosecutors accused Donald Trump of engaging in "criminal conspiracy and a coverup" as opening arguments began Monday in the first-ever criminal trial of a former US president.

Assistant District Attorney Matthew Colangelo said Trump falsified business records to pay $130,000 to porn star Stormy Daniels to "silence" her about a potentially politically embarrassing sexual encounter.

"This case is about a criminal conspiracy and a coverup," Colangelo told the jury of New Yorkers in a Manhattan courtroom.

"He orchestrated a criminal scheme to corrupt the 2016 presidential election."

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Trump, dressed in a dark suit and blue tie, sat at the defense table staring straight ahead as the prosecutor delivered his opening statement, shifting back and forth in his seat a little.

Before the court session began, Trump condemned the case as "election interference" designed to derail his 2024 White House bid.

"It's a very, very sad day in America," the 77-year-old Republican presidential candidate told reporters.

"I'm here instead of being able to be in Pennsylvania, in Georgia, and lots of other places campaigning... This is a witch hunt and it's a shame and it comes out of Washington."

Trump is the first former president to face criminal charges and the case poses substantial risks to him less than seven months before his election rematch with President Joe Biden.

Prosecution witnesses are expected to include Daniels and Trump's former fixer Michael Cohen.

The identities of the jury's five women and seven men are being kept secret for their own protection.

Trump faces 34 counts of falsifying business records to pay "hush money" to Daniels to ensure an account of their alleged 2006 extramarital tryst did not get out ahead of the 2016 election.

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The alleged crime is less significant than the indictments stemming from Trump's attack on the 2020 election – which the Republican lost to Democrat Biden – and his hoarding of secret documents.

Trump could face jail time in the hush money case, although a fine or probation is more likely, analysts say.