Trump says Bill Clinton should never have been impeached

US President Donald Trump speaks during a news conference at the World Economic Forum in Davos, Switzerland. AP Photo / Evan Vucci

US President Donald Trump has said he does not think former US President Bill Clinton should have been impeached at a press conference in the Swiss ski resort of Davos.

In an unscheduled media appearance before he was due to return to Washington on Wednesday, the US leader said he had only labelled his lawyer Ken Starr a "disaster" in the past because he was "sticking up for Bill Clinton."

"I have a great respect for Ken but I didn't think that Bill Clinton should have been impeached," he said. Starr also represented Bill Clinton at his impeachment trial in 1998 when he was acquitted.

Trump gave a keynote speech at the World Economic Forum in Davos, Switzerland just hours before his impeachment trial opened in the US on Tuesday and said he would "love to sit right in the front row and stare at their corrupt faces."

He said he would not consider delaying the State of the Union address because of the trial and blasted the press for what he claimed was unfair treatment.

"If we could straighten out the press in our country we would have a place that is so incredible," he said. "I deserve bad stories sometimes but when I do something great or good, let it be written about it."

Trump also said he would "love" to testify at his own impeachment trial.

Speaking to reporters at a ski resort on Wednesday, the leader branded Democrats "corrupt people [who are] playing the political game" in an episode that is "horrible for our country".

Trump also praised his personal lawyer Rudy Giuliani as a "high quality person" but said he didn't want the former New York mayor to represent him because he "didn't want there to be a conflict."

Questioned on whether he would attend the trial himself, Trump said he would "love to sit in the front row and stare at their corrupt faces".

The Senate will begin formal arguments when the trial convenes today (1pm ET), marking the start of what could be as much as 24 hours of opening arguments over three days.

The House managers will present their two articles of impeachment charging Mr Trump with abuse of power and obstruction of Congress.

Each of the seven House managers – who are serving as the prosecutors in the Senate impeachment trial – will address different elements of the case and seek to prove that the president committed high crimes and misdemeanors. They will have a chance to make their points without being challenged by either senators or the White House lawyers, who will get the opportunity to make arguments later.