The Pentagon said Thursday that plans to send some 3,000 troops to Afghanistan have been delayed by the need to use military transport planes to deliver relief supplies to hurricane-ravaged Puerto Rico.

The relief operation has resulted in a "slight delay" the Pentagon's plans to reinforce the 11,000 U.S. troops with additional forces, said Joint Staff Director Lt. Gen. Kenneth McKenzie, at a Pentagon briefing Thursday.

"It's a minor delay, there are still troops flowing in," added Dana White, the Pentagon's chief spokeswoman.

Defense Secretary Jim Mattis has already signed deployment orders for the additional military trainers but has said he would not discuss the details of the timing of troop movements because that information could be useful to the enemy.

In testimony before the Senate Tuesday, Mattis said demands of the Puerto Rican relief operations could affect the deployment of troops, not just in Afghanistan, but in other areas of the world.

"I assure you this is all hands on deck," Mattis told the Senate Armed Services Committee. "We are ready to go even to the point that it's going to impact the deployments, perhaps, of some of these troops overseas next year because we've interrupted their preparation."