Warren under fire, call for Trump impeachment at US Democratic presidential debate

At the first debate since Democrats in Congress launched an impeachment probe against Trump, the candidates defended the inquiry and said the president needed to be held accountable for his actions and for stonewalling Congress on its probe.

The investigation focuses on Trump's efforts to pressure Ukraine to investigate his unsubstantiated allegation that Biden improperly tried to aid his son Hunter's business interests in Ukraine.

Biden and Sanders both said that Trump was "the most corrupt president in history", and that Congress would be remiss if it did not pursue the impeachment probe.

"Impeachment is the way that we establish that this man will not be permitted to break the law over and over without consequences," Warren said.

Biden said Trump was going after him because he did not want to face him in next year's election.

"Look, my son did nothing wrong. I did nothing wrong. I carried out the policy of the United States government in rooting out corruption in Ukraine and that's what we should be focused on," Biden said. "What I think is important is we focus on why it's so important to remove this man from office."

Some Democrats warned that the party should bring Americans on board to support the probe. "We have to conduct this process in a way that is honorable," Booker said.

Most of the Democrats criticized Trump's abrupt decision to withdraw US troops from northern Syria.

The debate marked the return of Sanders, 78, the oldest candidate in the field, who suffered a heart attack two weeks ago and has been recuperating at home in Vermont since having stents inserted to open a blocked artery.

The health scare emphasized his age and that of the other top White House contenders - Biden is 76 and Warren is 70, while Trump is 73 - in a race featuring a debate about a generational change in leadership.

"We are going to be mounting a vigorous campaign all around this country," Sanders said, adding: "I'm so happy to be back here with you."

Reuters