When the House of Representatives returns to work Tuesday, don't expect an immediate announcement by Speaker Nancy Pelosi to send the articles of impeachment to the Senate.

The latest: A leadership aide tells Axios no decision has been made and that it may be a couple of weeks before Democrats can understand the significance of new revelations about Ukraine-related information being withheld by the White House — and whether at least four Republican senators are concerned enough to join forces with Democrats and demand more disclosures as part of President Trump's trial.

Why it matters: Some White House aides and Republican lawmakers bet the lack of movement with public sentiment and Senate Majority Leader Mitch McConnell, plus pressure on House and Senate Dems in vulnerable races, would prompt Pelosi to quickly cut bait after the holiday break.

But in recent days, revelations by Just Security about the president's personal involvement in holding back Ukraine assistance, and a New York Times Freedom of Information Act lawsuit that unearthed the existence of 20 undisclosed emails between top officials in the White House chief of staff's and budget offices, have only heightened Democrats' insistence on a "fair" trial with access to documents and witnesses.

Senate Minority Leader Chuck Schumer said on ABC's "This Week" that Pelosi "will maximize" the timing of sending the articles in order "to get the fairest trial possible." If she'd acted immediately, Schumer added, "McConnell could have well just voted for dismissal the day before or after Christmas." By waiting, "lots of new evidence that bolsters our case" has emerged for witnesses and documents.

The big question: How does the escalation of tensions and threat of war with Iran after the US killing of Iranian commander Qasem Soleimani affect the public's or lawmakers' appetite to extend the impeachment effort?

President Trump believes it strengthens his hand by allowing him to portray Democrats as choosing politics over more pressing national security.

But the shift in focus on Iran may buy Democrats more time and space to assess their next moves on impeachment.

Meanwhile, Democratic leaders have demanded more answers about the intelligence and justification behind the killing.

And House Intelligence Committee Chairman Adam Schiff (D-Calif.) on Sunday left open the possibility of a third article of impeachment.

What's next: Look for House and Senate Dems to gauge sentiment in their caucuses in the coming days. Look for Dems to lean on Republican senators like Lisa Murkowski of Alaska, Susan Collins of Maine, Cory Gardner of Colorado, Mitt Romney of Utah and Lamar Alexander of Tennessee to press McConnell to agree to some witnesses and document releases the White House is so far refusing.

Those GOP senators are either facing competitive re-elections fights, have previously expressed concerns about Trump's actions on Ukraine or are retiring and may feel freer to challenge the president. None is expected to convict.

Behind the scenes: A source familiar with the White House's impeachment strategy said they now don't expect Pelosi to send the articles over this week but they are "ready to go" whenever she does.

"The real question is what if she doesn't bring it?" the source said. "What we are looking at is what is her exit ramp?"

White House Counsel Pat Cipollone will lead Trump's defense in the Senate, this source said. And Trump's longtime private counsel Jay Sekulow will also play a role in the trial. Depending on Senate rules, House Republican members Doug Collins, John Ratcliffe and Jim Jordan may also participate in the trial.

The outside lawyer Alan Dershowitz, who got into Trump's good graces by saying nice things about him on Fox, is still being "highly considered" but may not end up participating, the source added.

The bottom line: We may not even hear much publicly from Pelosi on the matter until Thursday when she holds her weekly news conference, a leadership aide said.

Go deeper: Graham proposes changing Senate rules if Pelosi doesn't send articles of impeachment