In this April 27, 2020 photo, then US president Donald Trump (left) listens as then vice-president Mike Pence speaks about the coronavirus in the Rose Garden of the White House in Washington. (PHOTO / AP)

WASHINGTON – Former US vice-president and Republican presidential candidate Mike Pence said on Sunday he felt former president Donald Trump's words and actions leading up to the Capitol attacks on Jan 6, 2021, were reckless though not likely criminal.

Ahead of the 2021 Capitol attacks by Trump supporters, the then-president repeatedly lambasted Pence for refusing to try to prevent Congress from certifying Biden's win in the 2020 election

"While his words were reckless, based on what I know, I am not yet convinced that they were criminal," Pence told CNN's "State of the Union."

Trump said on Tuesday he had received a letter saying he is a target of a grand jury investigation into efforts to overturn his 2020 presidential election defeat.

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The letter represented the clearest sign to date that Trump, the front-runner for the 2024 Republican presidential nomination, may face federal criminal charges around his efforts to remain in power after losing the election to Democrat Joe Biden.

"I hope it does not come to that," Pence said on a potential Trump indictment over efforts to overturn the 2020 election. He said it should be left to the American public to determine whether Trump was responsible.

"His actions were reckless," Pence said. He added: "I don't honestly know what his intention was" on Jan 6, 2021.

Ahead of the 2021 Capitol attacks by Trump supporters, the then-president repeatedly lambasted Pence for refusing to try to prevent Congress from certifying Biden's win in the 2020 election.

Pence said on Sunday that Trump was wrong in thinking the former vice-president could overturn the outcome of the election. Some rioters chanted "hang Mike Pence" during the Capitol riots.

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"I know I did my duty that day," Pence said on Sunday.

Separately, Trump was indicted in June on charges that he unlawfully kept national security documents when he left office and lied to officials who sought to recover them. He has pleaded not guilty.

He was recently also charged with falsifying business records to conceal a hush money payment to a porn star.