Democratic House Speaker Nancy Pelosi has invited President Donald Trump to give evidence in front of investigators in the House impeachment inquiry ahead of a week that will see several key witnesses appear publicly.

Rejecting accusations from the president that the process has been stacked against him, Ms Pelosi said Mr Trump is welcome to appear or answer questions in writing, if he chooses.

“If he has information that is exculpatory, that means ex, taking away, culpable, blame, then we look forward to seeing it,” she said in an interview that aired Sunday on CBS’s Face The Nation.

Mr Trump “could come right before the committee and talk, speak all the truth that he wants if he wants”, she said.

Senate Democratic leader Chuck Schumer echoed that suggestion.

“If Donald Trump doesn’t agree with what he’s hearing, doesn’t like what he’s hearing, he shouldn’t tweet.

“He should come to the committee and testify under oath.

“And he should allow all those around him to come to the committee and testify under oath,” Mr Schumer told reporters.

He said the White House’s insistence on blocking witnesses from cooperating begs the question: “What is he hiding?”

The comments come as the House Intelligence Committee prepares for a second week of public hearings as part of its inquiry, including with the man who is arguably the most important witness.

Gordon Sondland, Mr Trump’s ambassador to the European Union, is among the only people interviewed to date who had direct conversations with the president about the situation because the White House has blocked others from cooperating with what they dismiss as a sham investigation.

And evidence suggests he was intimately involved in discussions that are at the heart of the investigation into whether Mr Trump held up US military aid to Ukraine to try to pressure the county’s president to announce an investigation into Democrats, including former Vice President Joe Biden, a leading 2020 candidate, and his son, Hunter.

Multiple witnesses overheard a phone call in which Mr Trump and Mr Sondland reportedly discussed efforts to push for the investigations.