Donald Trump faced fresh calls Sunday from some members of his own party to resign over the violent incursion into the US Capitol, as the threat builds for a historic second impeachment effort in his final 10 days in the White House.

With the January 20 inauguration of Democrat Joe Biden fast approaching -- and with the country hit by a surging pandemic, a flagging economy, and searing division -- resignation "is the best path forward," Republican Senator Pat Toomey told CNN, adding, "That would be a very good outcome."

Toomey said that since losing the November 3 election, Trump had "descended into a level of madness and engaged in activity that was absolutely unthinkable, and unforgivable."

US President Donald Trump faces pressure from his own party to step down
US President Donald Trump faces pressure from his own party to step down AFP / Brendan Smialowski

Democrats said some 200 of their lawmakers had lined up in favor of impeachment, with a vote in the House of Representatives possible as early as this week but a trial in the Senate possibly delayed for months to help Biden deal unimpeded with the nation's urgent problems.

Lisa Murkowski of Alaska was the first Republican senator to urge Trump's resignation, saying, "I want him out." House Republicans, including Adam Kinzinger on Sunday, have echoed that call.

The Federal Bureau of Investigation and other authorities are continuing to seek Trump supporters who violently stormed the Capitol on Wednesday after the president's repeated false claims that he had lost to Biden due to fraud. Dozens have already been arrested.

A protester carries a sign calling for Congress to impeach President Donald Trump near the US Capitol
A protester carries a sign calling for Congress to impeach President Donald Trump near the US Capitol AFP / Andrew CABALLERO-REYNOLDS

Hundreds of off-duty police on Sunday lined Constitution Avenue in Washington and saluted as a hearse rolled slowly by carrying the body of Brian Sicknick, the police officer who died in the chaotic attack on the Capitol.

Security has been stepped up in the aftermath of the attack. A seven-foot-tall (about two meters) black metal fence has been erected around the historic building. Extremists have threatened new action in coming days both in Washington and in state capitols.

Supporters of President Donald Trump forced their way into the US Capitol on January 6
Supporters of President Donald Trump forced their way into the US Capitol on January 6 AFP / Saul LOEB

A House Democratic leader said that Biden's party would likely file at least one article of impeachment against Trump this week, charging him with inciting the violence, which left five people dead, including a Capitol policeman.

"It may be Tuesday or Wednesday before action is taken," House whip James Clyburn told CNN, "but I think it will be taken this week."

National Guard soldiers stand guard outside buildings around the US Capitol
National Guard soldiers stand guard outside buildings around the US Capitol AFPTV / Daniel SLIM

Impeachment could still be circumvented by a Trump resignation or by resort to the constitution's 25th amendment, which would remove him from power but requires the assent of the vice president and most of the cabinet, making it unlikely.

One reason Democrats might pursue conviction, even after Trump leaves office, is to prevent him ever being able to run again for federal office.

The president has so far resisted all talk of resignation, and is reportedly furious over Pence's rejection of Trump's vocal pressure to somehow intervene in Congress's confirmation on Wednesday of Biden's election win.

Trump has gone largely silent in recent days -- making no statements and holding no news conferences. Twitter, his favored public platform, has banned him for language that could incite violence.

For now, the question of whether and when to impeach lies largely in the hands of House speaker Nancy Pelosi.

In an interview aired Sunday on CBS's "60 Minutes," Pelosi said, "I like the 25th Amendment, because it gets rid of him. He's out of office. But there's strong support in the Congress for impeaching the president a second time."

The Democratic-controlled House would be expected to approve the articles, but there were signs on Sunday that a Senate impeachment trial might not open for months.

Senate rules mean the upper chamber would likely be unable to open a trial before January 19, and Toomey said he was unsure it was constitutionally possible to impeach someone once out of office.

"Let's give President-elect Biden the 100 days" at the start of his term to deal with the most urgent issues, said Clyburn. "Maybe we'll send the articles some time after that."

And Senator Joe Manchin of West Virginia, a centrist Democrat whose vote could be crucial in the new, evenly divided Senate, told CNN an impeachment after January 20 "doesn't make any common sense whatsoever."