SYDNEY (AP) — Senior U.S. leaders expressed confidence that they will be able to convince allies to help protect shipping in the Persian Gulf area against Iranian threats, but they provided no new details Sunday on which nations may be willing to participate.

Defense Secretary Mark Esper says he has gotten a good response from allies and some announcements could be expected soon. And Secretary of State Mike Pompeo told reporters that a lot of conversations are taking place.

But after meeting with their Australian counterparts here, the two U.S. leaders came away with no commitment for help. Australian Defense Minister Linda Reynolds said her country is giving the U.S. request serious consideration but no decision has been made.

Called "Operation Sentinel," the plan has thus far attracted few commitments from other nations.