US plans 'more action' after striking militants in response to killing of 3 American troops

The U.S. will take "more action" against Iran-backed militants after a drone attack on an American base in Jordan, the White House's national security adviser said

After carrying out dozens of strikes in Iraq and Syria last week, the U.S. will take "more action" against Iran-backed militants in response to a deadly drone attack on an American base in Jordan, the White House's national security adviser said Sunday.

"This was the beginning of our response, there will be more steps," Jake Sullivan told ABC News "This Week" anchor George Stephanopoulos. "Some of those steps will be seen, some may not be seen. But there will be more action taken to respond to the tragic death of the three brave U.S. service members."

Late Friday, the U.S. launched its first round of retaliatory strikes in Syria and Iraq, hitting as many as 85 targets at seven facilities in less than 45 minutes, according to the U.S., which has blamed Iran-backed fighters for the attack on Tower 22 in Jordan on Jan. 28.

Defense Secretary Lloyd Austin said in a statement that the targets were being used by Iran's Islamic Revolutionary Guard Corps "and affiliated militias ... to attack U.S. forces."

Iran has denied involvement in the strike on Tower 22. Pressed by Stephanopoulos on Sunday whether additional retaliation could escalate tension with Iran, Sullivan said it's something the U.S. is prepared for.