US President Barack Obama is sending his defense chief next week to the Middle East, where he faces the unenviable job of reassuring allies such as Israel that a nuclear deal with Iran will not undermine America's commitment to their security.
It could be a very hard sell.
So far, the White House has only disclosed one stop on the trip - to Israel, where Prime Minister Benjamin Netanyahu condemned Tuesday's deal as "a stunning, historic mistake".
US defense officials told Reuters that Defense Secretary Ash Carter would travel elsewhere within the region but declined to offer details.
Offering a hint of his message to allies, Carter said in a statement about the Iran deal that the United States stood ready to "check Iranian malign influence".
Obama made a flurry of phone calls with regional allies on Tuesday, including with the crown prince of the United Arab Emirates and King Salman of Saudi Arabia. The White House said Obama stressed a commitment to work with Gulf partners to counter Iran's "destabilizing activities" and help them bolster their defense capabilities.