It came amid the Americans' most determined effort to reach a strategic rapprochement with its longtime adversary.
It's not yet clear what impact this might have on the negotiations that are picking up steam -- or on the discreet but growing effort by Israel to court the Arab states of the Persian Gulf to coordinate the anti-Iran stands they share.
The proposed arms deals, involving state-of-the-art warplanes, missiles and precision-guided munitions such as GBU-39 "bunker buster" bombs that would be needed to knock out Iran's nuclear facilities, come at a time of growing differences between Riyadh and Washington regarding Syria and Iran.
The lucrative contracts, first outlined in April, are welcome news for Lockheed Martin, Boeing Co., Raytheon and other U.S. defense giants, which are having to rely increasingly on exports amid severe cutbacks in military spending, not just in the United States but in Europe as well.
So there's a clear domestic gain for the U.S. defense sector. But some analysts view the arms sales as part of a U.S. effort to reassure Washington's Arab allies in the oil-rich gulf that they are not being abandoned as U.S. President Barack Obama focuses on his "Asian pivot" to meet the emerging Chinese challenge.
That suspicion of diminishing U.S. interest has been nurtured by the gulf monarchies since the Americans left their longtime Arab ally, Hosni Mubarak of Egypt, to his fate in the February 2011 pro-democracy uprising, and by the December 2011 U.S. withdrawal from Iraq, leaving it prey to Iranian expansionism.
The arms deals, under which Riyadh would be provided with weapons worth $6.8 billion and the Emirates $4 billion, demonstrate the extent to which U.S. arms exports have become a key element in Washington's Middle Eastern policy as its seeks to reduce its presence in the volatile region after decades of military domination.
"Recent events in the Middle East have diminished the overall political relationship between the two sides," observed the U.S. global intelligence consulting firm Stratfor.
"U.S. attempts at a negotiated solution with Iran as well as the U.S.-Russian deal on Syria have upset Saudi Arabia, the United Arab Emirates and other gulf countries" at a time when they feel threatened by the political turmoil sweeping the Arab world.
"In light of these differences," Stratfor noted, "the United States is increasingly relying on military and defense cooperation as the primary vehicle to maintain a close relationship with its gulf allies."
The new deals "bind the United States closer to Saudi Arabia and the United Arab Emirates. ...
"Military and defense cooperation is the one constant that Washington has used to maintain relations with -- and in the case of Egypt, occasionally pressure -- its Middle East allies," Stratfor added.
"At a time of diverging interests, when the United States is increasingly seeking a resolution with Iran despite its allies' concerns, such cooperation will be ever more important."
That should suit the U.S. defense sector just fine.
The list of hardware bound for the gulf includes 6,000 GBU-39/B small diameter bombs, the "bunker busters" built by Boeing -- 1,000 for Saudi Arabia and 5,000 for the Emirates, which gives some idea of who'll spearhead the air offensive against Iran if war breaks out.
There's also hundreds of air-launched Boeing Standoff Land Attack Missiles, or SLAM-expanded response weapons, and Raytheon's AGM-154C Joint Standoff Weapons, or JSOWs, that Arab jets can launch beyond the range of air-defenses.
Saudi Arabia will get 650 SLAM-ERs and 973 JSOWs, the Emirates 300 SLAM-ERs and 1,200 JSOWs.
However, the U.S. offer has been nuanced. The Pentagon reportedly refused requests by Riyadh and Abu Dhabi for Lockheed Martin's AGM-158 cruise missile designed to take out high-value targets, and Raytheon's High-Speed Anti-Radiation missiles to neutralize air-defenses.
"This decision may be less driven by the question of Iran than of Israel," observed Jean-Loup Samaan, a gulf security expert with the NATO Defense College.
"U.S. measures of reassurance to gulf countries still depend on the guarantee that they do not challenge Israel's qualitative military edge, a historical pillar of U.S. export policies in the Middle East."
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