The U.S. Pentagon notified Congress on Tuesday of a proposed sale to Israel of 100 guided bunker-busting bombs, a move that could prompt concerns about a unilateral Israel strike against Iran.

The GBU-28 bomb was developed for penetrating hardened command centers located deep underground.

John Isaacs, president of the Council for a Livable World, said the proposed sale was clearly ‘a provocative step’ that would prompt concerns about a unilateral Israel strike, particularly in Iran and elsewhere in the Middle East.

‘One could be suspicious that these bombs could be used for an Israeli attack on Iran,’ Isaacs said.

‘This particular munition is designed to destroy deeply buried high-value assets such as command centers or nuclear weapons facilities, so you can draw your own conclusion’ said Loren Thompson at the Virginia-based Lexington Institute.

Once notified, Congress has 30 days to reject planned foreign military sales but rarely does so, especially on military sales to Israel.