– House Speaker Nancy Pelosi on Sunday called on the Trump administration to promptly turn over a secret whistleblower complaint said to relate to President Donald Trump’s attempts to press Ukraine to investigate his leading Democratic presidential rival, warning that a refusal to do so could force the House to open a new phase in its investigation.

In a letter to fellow House Democrats, Pelosi never mentioned the word “impeachment,” but her remarks appeared to hint at the possibility that the newest revelations about Trump’s conduct — and the administration’s refusal to share the complaint with Congress — might be enough to prompt her and other leading Democrats to drop their resistance to moving forward with official charges against the president.

“If the administration persists in blocking this whistleblower from disclosing to Congress a serious possible breach of constitutional duties by the president, they will be entering a grave new chapter of lawlessness which will take us into a whole new stage of investigation,” Pelosi wrote in the letter.

The letter reflected a new level of urgency gripping Democrats amid news reports that Trump used a July phone call with the Ukrainian president to pressure the government there to investigate former Vice President Joe Biden’s son. The request is part of a secret whistleblower complaint that the administration has ordered be withheld from Congress.

Trump defends the call

On Sunday, Trump acknowledged that he discussed former Vice President Joe Biden with Ukraine’s president.

While Trump defended his July phone call with President Volodymyr Zelensky of Ukraine as perfectly appropriate, he confirmed that Biden came up during the discussion and that he accused the former vice president of corruption tied to his son Hunter’s business activities in Ukraine.

“The conversation I had was largely congratulatory, with largely corruption, all of the corruption taking place and largely the fact that we don’t want our people like Vice President Biden and his son creating to the corruption already in the Ukraine,” Trump told reporters before leaving for a trip to Texas and Ohio.

Trump did not directly confirm news reports that he pressured Zelensky for an investigation. The Wall Street Journal has reported that Trump urged Zelensky about eight times during the July 25 phone call to work with the president’s lawyer, Rudy Giuliani, on an investigation of Biden and his son.

Democrats’ quandary

The wording of Pelosi’s letter points to the deep quandary Democrats face on impeachment: As they encounter mounting evidence that many of them consider grounds for Trump’s removal, a political landscape has led many of them to conclude the endeavor would fail and potentially be disastrous. The reference to Trump’s duties under the Constitution and to “lawlessness” were nods to the severity of the situation, but Pelosi’s avoidance of the word “impeachment” strongly suggested that she was still resisting that course of action.

Pelosi urged Joseph Maguire, acting director of national intelligence who has stood in the way of the complaint getting to Congress, to relent by Thursday, when he is set to appear before the House Intelligence Committee in an open hearing. Maguire, in consultation with White House lawyers, has argued that he is not legally required to hand over the complaint.

Pelosi’s escalation was a significant one, and it came as progressives cranked up pressure on party leaders to take a more aggressive stance on impeachment and as even more moderate Democrats close to the speaker appeared to be warming to the possibility of that outcome. The House Judiciary Committee is already investigating whether to recommend articles of impeachment against Trump over other matters, but Pelosi has consistently questioned the strength of their case.

On Sunday, she asked Republicans to join Democrats in demanding that the whistleblower complaint be sent to Congress and that the as-yet-to-be-identified individual be allowed to speak with lawmakers. The inspector general, Michael Atkinson, has deemed the complaint a matter of “urgent concern and credible,” a designation that Democrats argue mandates that the administration share its contents with lawmakers.