WASHINGTON – Both the U.S. secretary of state and secretary of defense agreed Monday that North Korea represents the most urgent military threat to the United States during questioning by Colorado’s U.S. Sen. Cory Gardner.

Gardner is a member of the Senate Foreign Relations Committee, which held a hearing Monday to determine whether changes are needed to a law authorizing use of U.S. military force against its enemies.

Committee members said political threats have changed in the 16 years since the original law was enacted after the Sept. 11, 2001, terrorist attacks. They now include risks of nuclear war with North Korea.

North Korea has threatened the United States several times in recent months with nuclear missiles it is developing. President Donald Trump responded with threats of massive retaliation.

Gardner and other senators proposed legislation to ban organizations that deal with North Korea from doing business in the United States.

The sanctions approved by Congress this month and an executive order from Trump last month are supposed to punish North Korea and cut off supply lines for its military.

China is North Korea’s biggest trading partner. Some of its largest corporations are now blocked from trade with the United States.

“Are there more Chinese entities coming in the sanctions as it relates to North Korea?” Gardner, a Republican, asked Secretary of State Rex Tillerson.

Tillerson said the list developed by the U.S. Treasury Department is growing.

The Authorization for Use of Military Force approved by Congress in 2001 granted the U.S. military a right to attack conspirators in the Sept. 11, 2001, terrorist attacks and any “associated forces.”

The law granted the president authority to use “necessary and appropriate force” against al Qaeda, ISIS and their supporters, which led to a U.S. military presence in Afghanistan, Iraq and later Syria that has lasted 16 years so far.

Some members of the Senate Foreign Relations Committee said evolving strategies for regrouping by ISIS and growing North Korean hostility mean the law authorizing military force needs to be updated.

“What is the most significant rule of engagement change we’ve seen in our fight against ISIS?” Gardner asked.

Secretary of Defense James Mattis said the military is no longer restricted to engaging ISIS fighters within specific territorial limits.

“Wherever we see them, we can attack them,” Mattis said. “There is no need for [the U.S. military] to be in self-defense mode to call in air support.”

He credited the new strategy with much of the progress in suppressing ISIS military moves.

Congress has tried previously to replace the Authorization for Use of Military Force but failed over infighting between Democrats and Republicans on procedures for the law to take effect.

Tillerson and Mattis warned that any replacement law should not give an indication the United States was weakening in its military resolve.

“It would create significant new opportunities for our enemies to seize the initiative,” Tillerson said.

Political pressure for Congress to update its military force authorization heightened after four American soldiers were ambushed and killed this month in Niger by Islamic extremists. The U.S. has sent hundreds of military personnel to Africa as ISIS moves to other countries after recent defeats in Syria.

About 800 American soldiers are deployed in Niger as part of a French-led effort to combat extremists in West Africa.

The leading legislative proposal to revise the Authorization for Use of Military Force was sponsored by Sen. Tim Kaine, D-Va., and Sen. Jeff Flake, R-Ariz.

Flake expressed concern the current authorization could grant the president too much discretion to decide who and where to attack.

“We have to have a situation where Congress is more involved here,” Flake said.

Kaine said the military authorization for the Middle East is likely to face unforeseen challenges without updates.

“I think it’s a forever war,” Kaine said.