US HB4281

Authorizes the President to construct military infrastructure in Israel to accommodate large bunker-busting ordnance systems, including extended runways, aircraft capable of carrying the Massive Ordnance Penetrator (MOP), basing options, and munition storage facilities

Permits storing MOP weapons in Israel for U.S. use, with potential transfer to Israeli custody if Iran violates nuclear safeguards agreements, the President certifies it is vital to U.S. national security, Israel has no other means to destroy Iran's underground nuclear facilities, and a dual-key control system requiring presidential approval is in place

Authorizes training Israeli personnel on MOP-related munitions and conducting joint U.S.-Israel research to enhance ordnance capabilities for destroying underground infrastructure, including Hezbollah facilities and Iranian nuclear sites

Requires presidential certification to Congress that actions are vital to U.S. national security before exercising the authorities granted in the bill

Explicitly states the Act does not authorize the use of military force against Iran