"I'm not withholding them indefinitely. I'll send them over when I'm ready," Xinhua news agency quoted Pelosi as saying during her weekly briefing at the Capitol on Thursday, adding: "And that will probably be soon."
The Democrat-led House impeached Trump on December 18, 2019 for abuse of power and obstruction of Congress, charges that the President has rejected.
Pelosi, who initiated an impeachment inquiry into Trump in September 2019, is withholding the articles of impeachment and has refused to name impeachment managers, who will make the House's case in the Senate trial.
"As I said right from the start, we need to see the arena in which we are sending our managers. Is that too much to ask?" Pelosi queried.
Pressure is mounting on Pelosi, who is trying to give Democrats more leverage in setting rules for the trial in the Senate, where Republicans have a narrow majority, as some Democrats have urged her to send over the articles of impeachment.
"Our report accompanying the articles of impeachment says the president constitutes a clear and present danger to American constitutional system," Jamie Raskin, a Democratic member of the House Judiciary Committee, told reporters on Thursday.
"We have to move forward on a basis that does justice to what the Constitution provides," added Raskin.
Senate Majority Leader Mitch McConnell criticized Pelosi on Thursday, saying in a tweet: "This is a challenging time to create bipartisan agreement. But the Speaker Pelosi has managed to do the impossible.
"She has created growing bipartisan unity in opposition to her own reckless games with impeachment."
McConnell has said that the Senate should model Trump's impeachment trial after that of former President Bill Clinton, by dealing with potential witnesses after the trial begins.
Senate Minority Leader Chuck Schumer, however, has wanted to make sure certain witnesses would be called upon for the trial before it starts, which McConnell has so far rejected.
In an anonymous complaint last year, a whistleblower raised concerns about the White House's interactions with Ukraine, resulting in the Democrat-led impeachment inquiry against Trump.
The President was alleged to have pressed his Ukrainian counterpart, Volodymyr Zelensky, into launching investigations that could politically benefit him.
Furthermore, the White House allegedly tried to cover it up.
Having repeatedly denied any wrongdoings, Trump lashed out at the impeachment at the White House on Thursday, calling it "a hoax".
According to the nation's Constitution, the House has the sole power of impeachment, while the Senate can try all impeachments.
Conviction can only happen in the Senate and requires at least two-thirds of its members, or 67 Senators, to vote in favor after a trial.
Currently, the Senate has 53 Republicans, 45 Democrats and two Independents.
( With inputs from IANS )