On Wednesday afternoon, all 100 senators met with Secretary of State Rex Tillerson, Secretary of Defense Jim Mattis, Director of National Intelligence Dan Coats and Marine Corps. Gen. Joseph Dunford, chairman of the Joint Chiefs of Staff, for a classified briefing on the matter.
After the meeting, the top administration officials said President Donald Trump wants to pressure North Korea through tighter sanctions and diplomatic channels, but the United States is "prepared to defend" itself and allies.
Panetta believes the best course of action is for the U.S. to increase its presence in the area, support allies and continue to put pressure on China to try to get North Korea to the negotiating table.
He called national security Trump's greatest strength.
"He's got a great national security team. He's been willing to listen to them. And he's willing to change positions if necessary on China, on Syria, on NATO and some other areas," he said.
Meanwhile, Trump's weak point is dealing with Congress and getting any major legislation passed, Panetta said.
— CNBC's Jacob Pramuk contributed to this report.