The stockpile in Israel, which dates back to the 1990s, includes missiles, armored vehicles and artillery ammunition. The US military stores weapons in allied countries, including Israel, Gulf states and South Korea, as a precaution for possible operations.
The deal will double the value of military equipment kept on Israeli soil from 400 million to 800 million dollars, Major Shawn Turner told AFP.
Tensions with Iran over its nuclear program were not an impetus for the agreement, he said, noting that the US Congress initially authorized the expansion in 2007.
"This is not in any way related to Iran or the current situation as the authorization was from 2007," he said.
Washington's staunch ally Israel could have access to the weaponry and ammunition in an emergency but only with US approval, said a defense official, who spoke on condition of anonymity.