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House Speaker Nancy Pelosi, D-Calif., said Thursday that she will send the articles of impeachment against President Donald Trump to the Senate "when I'm ready," rebuffing calls from top Democrats to submit them.

“No, I’m not holding them indefinitely," Pelosi told reporters during a press conference at the Capitol. "I will turn them over when I’m ready, and that will probably be soon.”

Some Democrats in the House and Senate have joined Republicans in recent days in saying it's time for Pelosi to send the articles to the Senate.

After initially saying in an interview Thursday morning that he thought Pelosi should submit the articles, Rep. Adam Smith, D-Wash., backtracked, tweeting that he "misspoke."

The initial comments from Smith, chairman of the House Armed Services Committee, came as several Democratic senators this week called on Pelosi to send the articles to Senate Majority Mitch McConnell, R-Ky., so the impeachment trial can begin.

Adam Smith leaves the CVC Auditorium during a break in the House Democrats' organizational caucus meeting on Nov. 28, 2018. Bill Clark / CQ-Roll Call via Getty Images file

"I understand what the speaker is trying to do, basically trying to use the leverage of that to work with Democratic and Republican senators to try to get a reasonable trial, a trial that would actually show evidence, bring out witnesses," Smith told CNN. "But at the end of the day, just like we control it in the House, Mitch McConnell controls it in the Senate."

"I think it was perfectly advisable for the speaker to try to leverage that to get a better deal," he continued. "At this point, it doesn't look like that is going to happen. And yes, I think it is time to send the impeachment to the Senate and let Mitch McConnell be responsible for the fairness of the trial. He ultimately is."

Within hours, Smith walked back his remarks in a pair of tweets.

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"I misspoke this morning, I do believe we should do everything we can to force the Senate to have a fair trial," Smith tweeted. "If the Speaker believes that holding on to the articles for a longer time will help force a fair trial in the Senate, then I wholeheartedly support that decision."

"I am concerned that Senator McConnell won’t have a fair trial and I am with the Speaker that we should do everything we can to ensure he does," he continued. "Ultimately, I do want the articles sent to the Senate for the very simple reason that I want the impeachment process to go forward."

Democratic senators, such as Dianne Feinstein of California, Richard Blumenthal and Chris Murphy, both of Connecticut, have made similar comments in recent days.

"I don’t quite know what the strategy is," Feinstein told NBC News. "If you’re going to do it, do it. If you’re not going to do it, don’t."

"And obviously they’re going to do it, so I don’t understand the delay," she added.

Sen. Joe Manchin of West Virginia told NBC News, “The sooner we receive this, the sooner we can find out if we're going to have a real trial or not.”

But Feinstein, Blumenthal and Manchin said Thursday that the decision was up to Pelosi.

"I don't have a preference," Feinstein told NBC News when asked if she would like Pelosi to send the articles. "I mean, we have plenty to do, and the speaker will send them over when she's ready to send them over."

Blumenthal said when asked by NBC News about his previous comments, "What I’ve heard from my democratic colleagues is profound respect for the speaker’s decision. She has waited and the result has been additional evidence."

Pelosi has withheld the articles since her chamber adopted them last month, saying she will not transmit them to the Senate until the trial process is explicitly laid out. But she has suggested she could submit them soon.

"Nonetheless, at some point, we would hope that we would see from them what the terms of engagement will be," Pelosi told reporters Thursday. "We are ready, we are proud of our defense of the Constitution of the United States."

In a letter to colleagues Tuesday, Pelosi said it was important that McConnell "immediately publish this resolution, so that, as I have said before, we can see the arena in which we will be participating, appoint managers and transmit the articles to the Senate."

No trial can begin until the articles are sent.

McConnell has said he wants the Senate to conform to the procedure from President Bill Clinton's 1999 impeachment trial, which amounted to a two-step process: an initial agreement to hear the case and then a vote to decide whether to call witnesses.

Senate Minority Leader Chuck Schumer, D-N.Y., has pushed for a single resolution that would set parameters for presenting the case and calling witnesses. Schumer wants the Senate to call four witnesses to testify about Trump's Ukraine conduct, including former national security adviser John Bolton, who announced this week he would testify if subpoenaed, and acting White House chief of staff Mick Mulvaney.

McConnell, who in December vowed "total coordination" with the White House on the impeachment trial proceedings, said Tuesday he has the votes to set his desired process.

Last month, the House approved the two articles of impeachment against Trump, charging him with abuse of power and obstruction of Congress.

"PRESIDENTIAL HARASSMENT!" Trump tweeted Thursday morning, repeating a refrain that he and top Republicans have been using since Democrats took control of the House last year.