"If we are under attack, the president would have the authority under Article 2 to defend the country and there's no distinction between his authority to use conventional or nuclear weapons in response to such an attack", McKeon told lawmakers.
"This continues a series of hearings to examine these issues and will be the first time since 1976 that this committee or our House counterparts have looked specifically at the authority and process for using US nuclear weapons", Corker, who is from Tennessee, said in his statement.
In August, the national security adviser, HR McMaster, raised the prospect of a "preventative war", but many observers of the Korean standoff said any conflict was highly likely to quickly escalate into a nuclear exchange. The bill was first introduced by Senator Ed Markey, the Massachusetts Democrat, in September 2016, when Trump was only the Republican nominee and had not yet threatened "fire and fury" against a nuclear North Korea.
"We are concerned that the president is so unstable, is so volatile, 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. national-security interests", said Senator Murphy, explaining the reason for the public hearing.
The former commander of US Strategic Command, which oversees the Pentagon's nuclear arsenal, told Congress that in his previous role he would have followed the president's order to carry out a strike.
"The president would not make this decision by himself", said Brian McKeon, a former acting undersecretary for policy with the Department of Defense. But in a scenario where there is no imminent threat, top military officials can raise questions if they received an order they thought was illegal or hadn't been sufficiently vetted, retired Air Force Gen. C. Robert Kehler said.
The experts attempted to reassure senators there are processes in place to ensure many seasoned military and legal experts review nuclear orders before they are acted upon. Ben Cardin, followed, saying "we are dealing with a president. who has not seemed to be willing to accept advice on many issues affecting power".
But while some senators, including Democrat Edward Markey, expressed fear that in the age of Trump, an impulsive commander in chief has the power to unilaterally unleash a nuclear fusillade, the experts cautioned against legislative alterations that would broaden nuclear command authority to lower echelons.
For the first time in more than 40 years, the US Congress is examining the president's authority to launch a nuclear attack. 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.
Corker has broken publicly with Trump, warning last month that the president was setting the nation "on the path to World War III" with his statements about North Korea and verbal jousting with Kim. Corker has since been working with Sens. It does not have bipartisan support, however, and is unlikely to pass.
While the majority of the senators at the Senate Foreign Relations Committee avoided directly mentioning President Donald Trump by name, instead choosing to talk about a president's authority in general, Sens. James Risch, R-Idaho, said.
Democrats argued Trump is already confusing North Korea about the United States' intentions through his tweets. Jeanne Shaheen (D-N.H.).
"I would be very anxious about a miscalculation based on continued use of his Twitter account with regard to North Korea", Brian McKeon, a former acting undersecretary of policy at the Pentagon, testified.