The United States intelligence services and military worked with Israel to track the Iranian ship carrying missiles to Gaza, which was apprehended Wednesday, according to AFP.
White House spokesman Jay Carney said Washington started to work with Israel through intelligence and military channels and at the national security advisor level as soon as it knew the shipment was on the move.
President Barack Obama also directed the US military to work out contingencies in case it became necessary to intercept the vessel, White House spokesman Jay Carney told reporters aboard Air Force One.
"Throughout this time our intelligence and military activities were closely coordinated with our Israeli counterparts who ultimately chose to take the lead in interdicting this shipment of illicit arms," Carney said.
"We will continue to stand up to Iran's support for destabilizing activities in the region in coordination with our partners and allies," he said. "These illicit acts are unacceptable to the international community and in gross violation of Iran's Security Council obligations."
Israel said earlier that its forces intercepted the Syrian-made weapons, which were shipped overland to Iran and then onward towards Gaza by sea before being intercepted in the Red Sea between Sudan and Eritrea.
Defense Minister Moshe Ya'alon revealed earlier Wednesday that the missiles were heavy duty - with a range of 90 kilometers and with 175 kilogram warheads - and had the potential to threaten millions of Israelis. IDF Chief of Staff Benny Gantz revealed that the contents of the ships are being revealed to the press. Meanwhile, photos from the raid have been permitted for publication.