From Haaretz:

The American administration has rejected an Israeli request for military equipment and support that would improve Israel’s ability to attack Iran’s nuclear facilities.

[ . . . ]

The Americans viewed the request, which was transmitted (and rejected) at the highest level, as a sign that Israel is in the advanced stages of preparations to attack Iran. They therefore warned Israel against attacking, saying such a strike would undermine American interests. They also demanded that Israel give them prior notice if it nevertheless decided to strike Iran.

Shockingly responsible behavior on the Administration’s part.