For the first time in over 40 years, Congress is examining a US president’s authority to launch a nuclear attack.
The Senate Foreign Relations Committee hearing is titled Authority to Order the Use of Nuclear Weapons.
The panel’s Republican chairman accused President Donald Trump last month of setting the US “on a path to World War III”.
In August, Mr Trump vowed to unleash “fire and fury like the world has never seen” on North Korea if it continued to expand its atomic weapons programme.
The last time Congress debated this issue was over a four-day hearing in March 1976.