Washington DC - Former president Donald Trump’s conduct surrounding the January 6, 2021, siege of the US Capitol may have been criminal, Rep. Liz Cheney, a Republican vice-chair of the House committee probing the events, said on Sunday.

The House panel, which took the extraordinary step of subpoenaing the former president Friday, has detailed his efforts to overturn the results of the 2020 presidential election and his refusal to intervene when his supporters stormed Congress while lawmakers met to certify the election results, she noted.

"I think that there are multiple criminal offenses," Cheney told NBC’s Meet the Press. "I don’t want to get in front of the committee, but that’s what we are looking at."

The Wyoming Republican, who lost her reelection bid after taking on Trump, added: "Even if he thought that he had won, you may not send an armed mob to the Capitol."

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"You may not sit for 187 minutes and refuse to stop the attack while it’s underway. You may not send out a tweet that incites further violence," she said.

Last week, the nine-member panel gave Trump until "on or about" November 14 to begin testifying.

The former president reportedly has told people close to him that he would consider testifying if he could do so on live television.

Cheney did not say whether the committee would comply with such a condition.

"He’s not going to turn this into a circus," she insisted. "This isn’t going to be, you know, his first debate against Joe Biden and the circus and the food fight that that became … This is far too serious (a) set of issues."

Since the launch last year of the special committee, Trump has frequently attacked it and told former staffers to defy subpoenas.

"We have many, many alternatives that we will consider if the former president decides that he is not going to comply with his legal obligation – a legal obligation every American citizen has to comply with a subpoena," Cheney said.

A Trump-backed challenger defeated Cheney in Wyoming’s GOP primary in August. Though Cheney voted with Trump 93% of the time while he was president, she has been a vocal opponent to the ex-president's attempts to maintain power despite losing the 2020 election. Trump targeted her during this year's primaries over her vote to impeach him for inciting the January 6 insurrection, along with her leadership role on the House committee.

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Cheney faulted the Republican Party’s leadership for its handling of Trump. She said Senate Majority Leader Mitch McConnell of Kentucky has tried to ignore him while House Minority Leader Kevin McCarthy of California has embraced him.

"Obviously, the idea that we could simply ignore Donald Trump and the threat would go away is clearly wrong," she said.

"Leader McConnell has thought we can ignore him and go forward as a party without him continuing to have power and authority. That’s clearly not the case," she added.

The committee’s mandate expires in January, at the end of the current Congress.

Meanwhile, a Republican lawmaker said she wouldn’t rule out the idea of impeaching President Biden if the GOP takes control of Congress in next month’s midterm elections.

"That is something that would have to be investigated," said Rep. Nancy Mace of South Carolina.

She recently said Republicans were coming under pressure to impeach the president.

"I am not interested in playing tit for tat. I am not interested in retaliation," Mace said.