The United States said Wednesday its intelligence services and military worked with Israel to track a ship carrying an intercepted shipment of advanced Iranian rockets for Palestinian militants.
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.
The announcement came hours after Israel said it struck two Hezbollah fighters as they tried to plant a bomb near the Syrian-Israeli frontier and just over a week after Israel reportedly bombed the Iran-backed group inside Lebanon for the first time since 2006.
Israel has long accused Iran and Syria of providing military aid to Hezbollah and to Palestinian militant groups.
Israel latched onto the weapons shipment to chide Western powers for negotiating with Tehran over its nuclear program.
Iran said reports that it was involved in the shipment were without foundation.