Pelosi threatens to pursue impeachment if Trump’s cabinet does not strip him of powers.

The top Democrats in Congress called on Thursday for President Trump’s immediate removal from office for his role in urging on the violent mob that overtook the Capitol a day before, disrupting the ratification of President-elect Joseph R. Biden Jr.’s electoral victory.

Speaker Nancy Pelosi of California and Senator Chuck Schumer of New York called on Vice President Mike Pence to invoke the 25th Amendment, which allows him and the cabinet to wrest the power of the presidency from Mr. Trump.

If Mr. Pence declines to act, they said, Democrats were prepared to impeach Mr. Trump for a second time.

“While it’s only 13 days left, any day can be a horror show for America,” Ms. Pelosi said, calling Mr. Trump’s actions on Wednesday a “seditious act.”

The speaker’s plan was announced during an extraordinary news conference in the reclaimed Capitol, hours after the building was overrun by a mob of Trump supporters who temporarily halted Congress’s confirmation of Mr. Biden’s victory in the presidential election. Speaking to reporters, Ms. Pelosi singled out members of the cabinet by name, asking why they would not intervene.

“Are they ready to say for the next 13 days this dangerous man can assault our democracy?” Ms. Pelosi said of the cabinet.

She said she hoped to have an answer from Mr. Pence by the end of the day on whether he would attempt to use the 25th Amendment. The two leaders tried to call the vice president directly on Thursday but were left on a holding line for 20 minutes without him picking up. Mr. Pence is opposed to invoking the 25th Amendment, a person close to the vice president said Thursday evening.

It was unclear how quickly Democrats could move to impeach Mr. Trump. There is no clear precedent for putting a former official on trial in the Senate, and with only 13 days left in his term, it was not certain Democrats could actually accomplish such a complicated and politically fraught process on a compressed timetable.

Mr. Schumer, the top Democrat in the Senate, said: “What happened at the U.S. Capitol yesterday was an insurrection against the United States, incited by the president. This president should not hold office one day longer.”

Andrew Bates, a spokesman for the Biden transition, did not take a stand on the 25th Amendment or impeachment.

“President-elect Biden and Vice President-elect Harris are focused on their duty — preparing to take office on Jan. 20 — and will leave it to Vice President Pence, the cabinet and the Congress to act as they see fit,” Mr. Bates said. “In the meantime, Donald Trump must stop blocking cooperation with the transition that could harm the readiness of the United States government to overcome the pandemic and the other crises he has worsened.”