Defense Secretary Ash Carter is planning some major changes to how the military is organized in an effort to make it more agile and efficient, and more responsive to modern conflicts.

Carter on Tuesday previewed reforms he hopes to push forward this year to Goldwater Nichols, the 30-year-old law that governs how the military reports to the Pentagon and how geographic combatant commands are organized.

"It's time that we consider practical updates to this critical organizational framework, while still preserving its spirit and intent," Carter said in a speech at the Center for Strategic and International Studies.

One of the biggest changes would involve giving the chairman of the joint chiefs of staff more responsibility to coordinate, plan and move troops between geographic combatant commands while still remaining outside the chain of command to provide impartial advice to the president and the defense secretary.

This bolstered role of the chairman would allow for more agility in a complex security environment where threats are rarely confined to just one region, Carter said.

Critics of the current combatant command structure, which divides the world into geographic areas run by generals who report to the defense secretary, said that today's threats span the entire globe, as well as space and cyber realms. The fight against the Islamic State, for example, involves geographic commands in the Middle East, Europe and Africa, as well as special operators and cyber warriors.

Carter said he intends to make some changes to streamline the combatant command structure, but does not plan to consolidate geographic regions together like U.S. Northern Command and U.S. Southern Command, or the U.S. European Command and U.S. Africa Command.

"Instead of combining these commands to the detriment of our friends, our allies, and in fact our own command and control capabilities, we intend to be more efficient by integrating functions like logistics, intelligence, and plans across the Joint Staff, the combatant commands, and subordinate commands, eliminating redundancies wherever we find them without losing capability," he said.

Instead, some four-star leadership positions at combatant commands will be filled by three-star officers in the future to help streamline management at headquarters.

Carter also said that the department "should consider changes to cyber's role in DoD's Unified Command Plan," which suggests that he is at least open to elevating U.S. Cyber Command to the level of a geographic combatant command.

Troops trying to advance in their careers could also see some changes to the joint billet requirement, which requires service members to serve for three years in a billet that works with other services to discourage service rivalry.

These current requirements, however, are "more narrow and rigid than they need to be," Carter said. As a result, he is looking at shortening the requirement to only two years and expanding what roles would count toward that commitment.

Carter said the Pentagon will do what it can on its own and work with Congress on legislation for reforms that require a law change. The leaders of the armed services committees in both the House and Senate have said reforming Goldwater Nichols is a priority for them this year.