WASHINGTON – President Donald Trump suggested in a Fox News interview Friday that he would invoke executive privilege if former national security adviser John Bolton was subpoenaed for the Senate impeachment trial.

Bolton said earlier this week that he is "prepared to testify" in the trial – if he's subpoenaed by the Republican-controlled chamber.

"I have concluded that, if the Senate issues a subpoena for my testimony, I am prepared to testify," Bolton stated.

Fox News anchor Laura Ingraham asked the president in an interview whether he would block Bolton from testifying.

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"You can’t be in the White House as president — future, I’m talking about future, any future presidents — and have a security adviser, anybody having to do with security, and legal, and other things," Trump said.

"Are you going to invoke executive privilege?” Ingraham asked pointedly.

“Well I think you have to for the sake of the office,” Trump replied.

House Speaker Nancy Pelosi said Friday that the House will send articles of impeachment against Trump to the Senate next week, paving the way for a trial in the Senate to begin.

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Pelosi delayed sending the articles, which accuse Trump of abuse of power and obstruction of Congress, since the House approved them Dec. 18. She said she wanted to know more about how the Senate would conduct its trial, including the state of new witnesses and evidence, before naming the lawmakers to serve as managers.

Senate Majority Leader Mitch McConnell, R-Ky., has said he plans to move quickly to begin a trial once he has received the articles from the House. He has rejected demands from Democrats to approve witnesses before the trial.

A decision on witnesses would be made during the trial, rather than before it began, he said.

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Trump has addressed Bolton potentially testifying before. A few days ago, the president dismissed the possibility that Bolton's testimony would be of any significance, claiming that his former national security adviser "would know nothing about what we're talking about."

However, Bolton has hinted that he could offer new details about the Ukraine pressure campaign, and was personally mentioned by many of the witnesses that testified in the House's inquiry and trial.

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For example, Fiona Hill, a former National Security Council official, described in her testimony how concerned Bolton was by the linkage of aid and investigations.

When U.S. Ambassador to the European Union Gordon Sondland brought up investigations into the Biden's and the 2016 elections during a meeting between American and Ukrainian officials on July 10, Hill testified recalling Bolton telling her it was like a "drug deal" and urged her to brief National Security Council lawyers.

In November, Bolton defied a request from Democrats leading the House impeachment inquiry to testify. At the time, Bolton's lawyer told lawmakers he would take the impeachment committee to court if it subpoenaed him.

House Democrats decided not to subpoena Bolton during their probe, arguing it would delay their investigation with a protracted court battle; instead, they labeled Bolton's refusal to appear as evidence of obstruction.

Senator Susan Collins, R-Maine, reportedly said Friday that she's been working with "a fairly small group" of fellow Republicans to ensure that witnesses can be called, explaining that "We should be completely open to calling witnesses," according to Bangor Daily News.

Contributing: Deirdre Shesgreen, David Jackson, Ledyard King, Christal Hayes, Nicholas Wu, Bart Jansen, USA TODAY