"In an impeachment trial, every Senator takes an oath to 'do impartial justice according to the Constitution and laws.' Every Senator now faces a choice: to be loyal to the President or to the Constitution", she wrote.
For five senators who are running for the Democratic presidential nomination, the impeachment trial complicates the face-to-face contact that's critical for candidates before the February 3 Iowa caucuses.
Pelosi's announcement comes approximately three weeks after the House voted to impeach President Trump on two counts: abuse of power for allegedly withholding hundreds of millions of dollars in aid to Ukraine in exchange for an in investigation into a top political rival, and obstructing congress in their attempt to investigate that abuse. An Aug. 30 email leaked to the public quoted a White House budget official telling the Pentagon that it was "clear direction from POTUS to hold" military assistance for Ukraine despite repeated warnings that doing so was probably illegal.
The Senate has been in waiting mode as it can't formally begin its trial until the impeachment articles are transmitted.
On Thursday, representative Adam Smith (D., Wash.) Told CNN that Pelosi should send the articles to the Senate.
Nadeam Elshami, Pelosi's former chief of staff, said he thinks she got what she wanted.
Mr McConnell told House Republicans he expected to get the articles as early as today which would set up a trial for next week.
Mr Trump is the third president in United States history to be impeached.
The Republican leader has neither shared text of a trial resolution with Mr Trump nor negotiated with the White House on how the measure would be worded. Democrats, including Pelosi, have argued the strike lead to furthering tensions with the Persian nation.
When she's ready: At her weekly news conference Thursday, Pelosi suggested her hold on the articles of impeachment did not specify the circumstances that would lead to her releasing the articles to the Senate.
Pelosi has declined to submit the charges, or articles of impeachment, to the Senate. He replied that these decisions would be made later - by the Republican-controlled Senate, not by anyone in the democratically run house.
McConnell, who has criticized Pelosi's moves, has said that the Senate should model Trump's impeachment trial after that of former President Bill Clinton's case in 1999 by dealing with potential witnesses after the trial begins.
"Has nothing to do with the validity and urgency of these impeachments, but rather with assuring the American people that we will have a Senate trial and not just an unfair vote", said Sewell (D-AL).
"I'd like to hear what John Bolton has to say", said Sen. There is no evidence of wrongdoing by either Biden.
But especially a national security adviser, you can't have him explaining all of your statements about national security concerning Russia, China, North Korea, everything.
Democratic senators, meanwhile, urged Pelosi to quit stalling.
But her announcement indicates the Senate will have the articles by the end of next week, meaning the upper chamber could begin President Trump's trial shortly there after.