Turkey has agreed to let the U.S. train Syrian rebels on its soil to fight Islamic State extremists and open its military bases to coalition forces, U.S. National Security Adviser Susan Rice said.

The agreement is a significant expansion of Turkish cooperation in the fight against Islamic State, which has declared a caliphate in parts of Syria and Iraq and is gaining territory along the Turkish border.

While Turkey has previously pledged to join the campaign, it hadn’t said what it would be willing to contribute militarily. The NATO member had ruled out sending ground troops into Syria unless the U.S. led a broader campaign to oust Syrian President Bashar al-Assad.

Turkey is now willing to join Saudi Arabia in offering territory to be used to train moderate Syrian rebels who could fight Islamic State on the ground in Syria, Rice said on NBC’s “Meet the Press” program that aired today.

The U.S. has ruled out sending its own ground troops into Syria and Iraq.

Rice also said Turkish bases could be used by coalition forces. Such a move would give U.S. aircraft close access to targets in neighboring Syria. The U.S. has an air base near Incirlik, Turkey.

While Turkey has pressed the U.S. to establish a “buffer zone” and no-fly zone in Syria, Rice said there are no plans to do so.

“We don’t see it at this point as essential to the goal of degrading and ultimately destroying ISIL,” she said, using an acronym for Islamic State.