Amid concerns over President Trump’s temperament, a Senate panel examined Tuesday the question of whether the president should have the sole power to launch a nuclear strike.

The exceedingly rare hearing by the Senate Foreign Relations Committee came after Trump threatened North Korea with military force, including his declaration that Pyongyang would be met with “fire and fury like the world has never seen.”

The authority to launch a nuclear strike has remained with the White House since President Truman ordered dropping atomic bombs over Hiroshima and Nagasaki during World War II. Indeed, a military aide shadows the commander in chief day and night, carrying the black briefcase commonly referred to as the “nuclear football,” packed with attack options and other information needed in a national emergency.

The decision to launch a nuclear attack is made by the president, relayed to the nation’s top uniformed military officer, known as Chairman of the Joint Chiefs of Staff, before it sent down the chain of command, according to military documents. The order from the president would unleash the world’s most powerful nuclear arsenal either through a fleet of strategic bombers or missile-launching submarines or land-based intercontinental ballistic missiles.

The quick-reaction system was designed during the Cold War to put the nuclear forces on hair-trigger alert, given that a Soviet Union attack could obliterate the nation’s defenses – and leadership – in 30 minutes or less. Many in Congress believe there should be a mechanism for the president to get their approval before launching.

The issue is particularly concerning to Congress because of heightened tensions with North Korea and the war of words between the nations’ leaders. An American preemptive nuclear attack on Pyongyang would almost certainly result in the deaths of millions due to a strike and North Korean counterattack against regional allies Japan and South Korea.

Read More: Here’s What Donald Trump Has Said About Nuclear Weapons

Republican Sen. Bob Corker of Tennessee, the powerful chairman of the Senate Foreign Relations Committee, said during the hearing was needed for Congress to explore “the realities of this system.”

“Making the decision to go to war of any sort is a heavy responsibility for our nation’s elected leaders,” Corker said. “And the decision to use nuclear weapons is the most consequential of all.”

He said it was the first time a hearing on the topic had taken place since 1976, which was after it became known that President Nixon was frequently drunk and depressed in the waning days of his administration.

Corker publicly questioned Trump’s decision-making abilities last month when he expressed concern over the president’s heated rhetoric that, in his view, undermined U.S. diplomatic efforts with foreign adversaries and put the country “on the path to World War III.”

Democratic Sen. Chris Murphy of Connecticut seemed to agree during the hearing when he addressed the panel.

“We are concerned that the President of the United States is so unstable, is so volatile, and has a decision-making process that is so quixotic that he might order a nuclear weapons strike that is wildly out of step with U.S. security interests,” he said. “So let’s just recognize the exceptional nature of this moment, of this discussion we’re having today.”

The Democrats have already drafted a bill that calls for the president to obtain a declaration of war from Congress before he or she can first launch a nuclear strike. It does not have bipartisan support, however, and is unlikely to pass.

C. Robert Kehler, the retired Air Force general who commanded U.S. Strategic Command, which oversees the nation’s nuclear arsenal, told the committee there are military checks on the president who orders a nuclear strike if the U.S. is not first under attack.

“If there is an illegal order presented to the military, the military is obligated to refuse to follow it,” he said.

Brian McKeon, former acting under secretary for policy at the Pentagon during the Obama Administration, told the committee that the president would have to come to Congress for approval in the event of a first strike, but not in the event of a retaliatory strike. Even then, the president is not likely to “make this decision by himself.”

“He would require lots of people cooperating with him to make the strike happen,” McKeon said. “They’d be asking questions that would slow down that process.”

Stephen Schwartz, a nuclear weapons policy expert and the editor of “Atomic Audit,” which assesses the costs of the U.S. nuclear weapons program, said in an interview that the nation is closer than it ever has been in the post-Cold War era to a miscalculation that could lead to nuclear war.

“It boggles the mind that there is not at least one Constitutional office holder that has to be consulted before a nuclear strike is ordered,” he said. “The process was probably necessary during the Cold War, but that time has long passed and now it’s worthy of continued review.”

Correction: The original version of this story misattributed remarks by Stephen Schwartz at Tuesday’s hearing to C. Robert Kehler. The story has been updated with a correct quote from Kehler.

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Write to W.J. Hennigan at william.hennigan@time.com.