WASHINGTON, Oct. 30 (Xinhua) -- U.S. Secretary of State Rex Tillerson said Monday that the Trump administration was not seeking a new war authorization from Congress for overseas military operations against terrorist groups.

"The United States has the legal authority to prosecute campaigns against the Taliban, al-Qaida and associated forces, including ISIS (the Islamic State), and is not currently seeking any new or additional congressional authorization for the use of force," Tillerson said here at a congressional hearing.

Under the U.S. Constitution, only Congress has the power to declare war.

U.S. lawmakers were said to be considering updating or repealing the 2001 Authorization for Use of Military Force (AUMF), which authorizes the use of U.S. armed forces against those responsible for the attacks on Sept. 11, 2001 and any associated forces.

Tillerson said the AUMF "remains a cornerstone for ongoing U.S. military operations and continues to provide legal authority relied upon to defeat this threat."

Speaking at the same hearing, U.S. Defense Secretary Jim Mattis said that a new AUMF was "not legally required" to address the threat posed by terrorist groups.

While he was not averse to a new AUMF, Mattis said that any new AUMF must not be time-restricted.

"War is fundamentally unpredictable. We cannot put a firm timeline on conflict against any adaptive enemy who would hope that we haven't the will to fight as long as necessary," Mattis said.