A former Republican senator is calling on Congress to remove President Donald Trump from office because he believes Trump’s “sick psyche” dramatically increases the odds of nuclear war.

Gordon Humphrey, who represented New Hampshire for two terms in the US Senate from 1979 until 1990, published an open letter on Thursday urging his state’s congressional delegation to support the Oversight Commission on Presidential Capacity Act, which would create a commission to determine whether the president is mentally fit.

“Literally, [Trump] could get millions of people killed if he’s not restrained,” Humphrey said on MSNBC Thursday night.

Your browser does not support HTML5 video.

Earlier in the day, Humphrey — who quit the GOP after Trump’s election — published a letter in the Concord Monitor arguing the same points:

Donald Trump is impaired by a seriously sick psyche. His sick mind and reckless conduct could consume the lives of millions. The threat of nuclear war is steeply on the rise. You must not take comfort in the system of checks and balances. The president alone has the authority to launch nuclear weapons, the only restraint being the advice of senior advisers who might be present at the time of crisis, and Donald Trump has shown repeated contempt for informed and wise counsel. He is sick of mind, impetuous, arrogant, belligerent and dangerous. Donald Trump should be relieved of the powers of the presidency at the earliest date. ... Serious crises are bearing down on us. We cannot leave our national security and our families’ safety in the hands of a president whose poor judgment, belligerence, vindictiveness and reckless impetuosity constitute an indictment of his mental health. Donald Trump is seriously sick. He is dangerous. As a citizen, a former U.S. senator and 12-year member of the Armed Services Committee, I urge you to act once. This is an emergency.

On MSNBC, Humphrey also urged the US Cabinet and Vice President Mike Pence to consider using the 25th Amendment to expel Trump from office. Section 4 of that amendment allows the Cabinet and vice president to remove Trump if they determine he is “unable to discharge the powers and duties of his office.”

"Congress and the Cabinet should be talking seriously about his fitness,” Humphrey told MSNBC’s Lawrence O’Donnell, arguing Trump had brought America to the brink of nuclear war. “They're saying behind scenes, 'He's crazy ... he's delusional, he's paranoid, he's not a well man. He's dangerous.’"

Trump has, so far, not responded.