U.S. President Donald Trump said Thursday he will shift his focus to ensuring a "smooth" transition of power to President-elect Joe Biden amid growing calls for his removal from office for inciting a violent takeover attempt of Capitol Hill by his supporters.

"A new administration will be inaugurated on Jan. 20. My focus now turns to ensuring a smooth, orderly and seamless transition of power," Trump said in a video message posted on Twitter, adding, "Serving as your president has been the honor of my lifetime."

U.S. President Donald Trump speaks at "Save America March" rally in Washington, United States on Jan. 6, 2021. (Anadolu Agency/Getty/Kyodo)

Some U.S. media said the latest statement amounted to a concession following continuing refusal to admit his defeat in the Nov. 3 election, having claimed widespread voter fraud without substantial evidence.

The Trump supporters who stormed the Capitol on Wednesday apparently sought to obstruct Congress from certifying Democrat Biden's win, emboldened by the Republican president's call during a rally in Washington earlier in the day to "walk down" to the building to demand lawmakers reject the election outcome.

Trump said in the video message that the demonstrators who breached the Capitol "defiled the seat of American democracy" and those who engaged in violence and destruction "do not represent our country."

But it is uncertain whether the latest development will help address concerns growing inside the country that he is no longer fit to serve as president, even for the remainder of his term.

Earlier Thursday, Democratic leaders in both the House of Representatives and the Senate called for Trump's ouster via invocation of the 25th Amendment of the Constitution, a protection mechanism for the government against the dangers of an incapacitated president.

A mob loyal to U.S. President Donald Trump gathers near the U.S. Capitol in Washington on Jan. 6, 2021. The move came after Trump urged his supporters to descend on Washington to protest Congress' impending certification of Joe Biden as the winner of the November presidential election. (Kyodo) ==Kyodo

"What happened at the U.S. Capitol yesterday was an insurrection against the United States, incited by President Trump," Sen. Chuck Schumer said in a pair of tweets. "The quickest and most effective way -- it can be done today -- to remove this president from office would be for the Vice President to immediately invoke the 25th amendment."

"If the Vice President and the Cabinet refuse to stand up, Congress must reconvene to impeach President Trump," he added.

Trump, 74, was already impeached in December 2019 by the Democrat-controlled House when it brought accusations that he abused the power of his office to boost his own chances of re-election. He was acquitted in a subsequent trial in the Republican-controlled Senate.

The 25th Amendment sets forth succession rules relating to vacancies in the event of a president's inability to carry out the duties of the office. It allows for the vice president and a majority of the Cabinet to declare the president unfit for office, enabling the vice president to become acting president.

House Speaker Nancy Pelosi said she is expecting a swift decision from Vice President Mike Pence on whether he will resort to the 25th Amendment.

A mob loyal to U.S. President Donald Trump gathers near the U.S. Capitol in Washington on Jan. 6, 2021. The move came after Trump urged his supporters to descend on Washington to protest Congress' impending certification of Joe Biden as the winner of the November presidential election. (Kyodo) ==Kyodo

"I don't think that it'll take long to get an answer from the vice president. It will be yes, it will be no. And then we'll see," she told a press conference.

U.S. media reported it is unlikely that Pence will pursue the path of invoking the 25th Amendment at this point.

Republican Rep. Adam Kinzinger posted a video message on Twitter calling for the 25th Amendment to be invoked to ensure that "the next few weeks are safe for the American people."

"Sadly yesterday it became evident that not only has the president abdicated his duty to protect the American people and the people's house, he invoked and inflamed passions that only gave fuel to the insurrection that we saw here," he said.

"When pressed to move and denounce the violence, he barely did so...it's time to invoke the 25th amendment and to end this nightmare," Kinzinger added.

More of Trump's aides are also breaking off from the president, with Transportation Secretary Elaine Chao becoming the first Cabinet member to announce her resignation following Wednesday's chaotic incident.

Chao said in a statement posted on Twitter she was "deeply troubled" with the "traumatic and entirely avoidable event" that took place as Trump supporters stormed the Capitol building following a rally he addressed. She said she will resign on Monday.

Education Secretary Betsy Davos has also said she was resigning, The Wall Street Journal reported later Thursday.

According to CNN, a Capitol police officer has died from events stemming from Wednesday's riot, raising the total death toll from the incident to five.

The five include a woman who was fatally shot by police inside the Capitol as protesters were forcing their way toward an area where Congress members were sheltering in place, the police said.