Defense Secretary Ash Carter signaled Wednesday that the U.S. military will expand efforts to target Islamic State militants beyond the group's territory in Iraq and Syria, potentially involving air strikes and raids in other Islamic countries.

"The threat posed by ISIL, and groups like it, is continually evolving, changing focus and shifting location," Carter said, using an alternative acronym for the Islamic State group.

"That’s why the Defense Department is organizing a new way to leverage the security infrastructure we’ve already established in Afghanistan, the Middle East, East Africa, and Ssouthern Europe into a network to counter transnational and transregional threats like ISIL," Carter said.

"They help us act decisively to prevent ISIL affiliates from becoming as great of a threat as the parent tumor itself," Carter said.

For example, Carter pointed to a U.S. airstrike in Libya in November that killed a man known as Abu Nabil, an Iraqi national who was a senior Islamic State leader in Libya.

The U.S. has also begun targeting some Islamic State militants in Afghanistan.

Although Congress has not passed any new authorities for striking the Islamic State group, the Obama administration says prior laws passed after 2001 clear the way for U.S. troops and aircraft to strike at Islamic State targets in many countries.

"We have made it clear that those who threaten or incite harm to Americans, wherever they are, will surely come to feel the long arm and the hard fist of justice," Carter said.

Among the troops Carter spoke to were some of the 1,300 soldiers who will be deploying to Iraq this spring from the 101st Airborne Division's 2nd Brigade Combat team. They will be advising and assisting the Iraqi Security Forces, replacing soldiers from the 10th Mountain Division who are there now.

"I am asking you to take on this challenge," Carter told the deploying soldiers.

"The Iraqi and Ppeshmerga forces you will train, advise and assist have proven their determination, their resiliency, and increasingly, their capability. But they need you to continue building on that success, preparing them for the fight today and the long hard fight for their future," Carter said.

"They need your skill. They need your experience. Often, they will need your patience," he said.

There are currently about 3,500 U.S. troops in Iraq.

Carter also encouraged the rank-and-file troops to contribute to the evolving campaign plan.

"I encourage you to bring fresh ideas and new perspectives to the fight ... You will see things that we don't see in Washington — and things your commanders might not see," Carter said.

"Tell your commanders, so they can tell me. We must maintain the tactical flexibility to take full advantage of these opportunities as they emerge, even as our basic strategy remains in place, and that depends on you," Carter said.