When asked before the hearing if he was concerned about Trump's authority, Corker said, "This is not specific to anyone".
Bob Corker, the Republican chairman of the chamber's foreign relations committee, has expressed fears that the president was taking the country "on the path to world war III". "I don't think the assurances I've received today will be satisfying to the American people".
Another senator on the panel has drafted legislation proposing to curb the president's power to launch a nuclear attack.
But they acknowledged that the President could overrule the advice of his advisers and order a nuclear strike if it is deemed lawful.
"We are concerned that the President of the United States is so unstable, is so volatile, has a decision-making process that is so quixotic, that he might order a nuclear weapon strike that is wildly out of step with U.S. national security interests", Connecticut Democrat Chris Murphy said.
In August, Trump issued an apocalyptic threat to unleash "fire and fury" on North Korea and he took to calling Kim "Rocket Man" after a series of provocative missile tests.
Amid growing anxiety that President Donald Trump's heated rhetoric could trigger a war with North Korea, lawmakers on Tuesday debated for the first time in 40 years a United States president's authority to launch a nuclear strike. In recent months, lawmakers have insisted the president seek Congress's approval before revoking any sanctions against Russian Federation, and momentum is building for a new authorization for use of military force (AUMF) to address the military's current and future operations against the Islamic State and other extremist groups. Even then, the president is not likely to "make this decision by himself".
On Tuesday, former officials cautioned that adding Congress to the equation would hamper the United States response in a high-stress scenario without a lot of time.
Adding the extra layer would lead to "conflicting signals" that "can result in loss of confidence, confusion or paralysis in the operating forces at a critical moment", Kehler said.
Military experts testifying before the committee noted that, while presidents have ultimate authority to order nuclear strikes, there are safeguards in place to ensure those orders are considered first. Gerald Ford was president.
Under the USA constitution, only Congress has the power to declare war, but the president, as commander-in-chief of the armed forces, has the authority to respond to an actual or imminent threat. The deterrent strength of a nuclear arsenal is not only in its ability to strike anywhere, but in the ability of the Commander-in-Chief to expeditiously make that decision.
Acknowledging that the president has the sole authority to give the order to launch a nuclear strike "whether we are responding to a nuclear attack or not", Corker said he hoped the hearing would allow his committee "to explore the realities of this system".
While the President retains constitutional authority to order some military action, Kehler explained that the nuclear decision process "includes assessment, review and consultation between the President and key civilian and military leaders, followed by transmission and implementation of any Presidential decision by the forces themselves". In this scenario, Mattis, national security adviser Lt. Gen. H.R. McMaster and Secretary of State Rex Tillerson are not part of the chain of command.
Senator Chris Murphy (D-CT) introduces Dr. Scott Gottlieb before a Senate Health Education Labor and Pension Committee confirmation hearing on his nomination to be commissioner of the Food and Drug Administration on Capitol Hill in Washington, D.C., U.S., April 5, 2017.
"One of the things that voters think about" in United States presidential elections, Rubio said, "is whether or not they want to trust him with this capability".