WASHINGTON (NewsNation Now) — In a letter to her Democratic colleagues about this week’s attack on the Capitol, House Speaker Nancy Pelosi described her efforts to prevent President Donald Trump from initiating military actions or a nuclear strike.

Pelosi said that she has spoken to the chairman of the Joint Chiefs of Staff, Gen. Mark Milley, ahead of a conference call with the House Democrats Friday to consider impeachment proceedings against the president. A person familiar with the call says Pelosi told them that Milley told her there are precautions in place that would prevent such an action by Trump.

The president has sole authority in the U.S. government to order the launch of a nuclear weapon. But if a military commander were to determine, on advice of his lawyers, that such an order was illegal, then the order could be refused.

It would be illegal to launch a nuclear attack for no reason or as a disproportionate response to a military provocation.

The person described Friday’s conference call on condition of anonymity because the call was limited to House Democrats.

In her letter to lawmakers Friday, Pelosi wrote, “The situation of this unhinged President could not be more dangerous, and we must do everything that we can to protect the American people from his unbalanced assault on our country and our democracy.”

Milley’s office said that Pelosi had initiated the call and that the general “answered her questions regarding the process of nuclear command authority.”

The letter also addressed the storming of the Capitol by pro-Trump rioters, the death of a U.S. Capitol police officer and calls to remove President Trump from office.

Pelosi and Democratic Senate leader Chuck Schumer have called on Vice President Mike Pence and the Cabinet to invoke the 25th Amendment to force Trump from office. It’s a process for removing the president and installing the vice president to take over.

Pelosi also said Friday that she had not heard back from Pence about whether he would agree to invoke the 25th Amendment.

“We still hope to hear from him as soon as possible with a positive answer,” she said.

Pence is opposed to such a move, an adviser told Reuters on Thursday.

Even if the House impeaches Trump at such short notice, the decision on whether to remove him would fall to the Republican-controlled Senate, which has acquitted him once before. With Trump’s term ending Jan. 20 and the Senate scheduled to be in recess until Jan. 19, the prospects of an actual ouster appear unlikely.

Removing a U.S. president requires a two-thirds majority in the Senate. Republican Senate Majority Leader Mitch McConnell has not commented on a possible impeachment.

Democratic President-elect Joe Biden takes office on Jan. 20. Trump said earlier on Friday he would not attend the inauguration, breaking with long-standing tradition in American presidential transitions.