WASHINGTON - Qatar and the United Arab Emirates have requested the sale of up to $7.6 billion in Lockheed Martin Corp missile-defense systems to counter perceived threats and lower their dependence on US forces, the Pentagon announced on Monday.The sale is part of Washington's ongoing effort to deepen its cooperation with Gulf nations on missile defense and increase pressure on Iran over its nuclear program.US goal is development of "regional shield" On Monday, the Pentagon said Qatar had requested the possible sale of two THAAD fire units, 12 launchers, 150 interceptors, parts, training and logistical support for an estimated cost of $6.5 billion.The UAE, which signed an initial order for $1.96 billion of THAAD weapons systems in December, requested an additional 48 THAAD missiles, 9 launchers and other equipment valued at $1.135 billion, according to a DSCA notification.It said the proposed sale would contribute to the foreign policy and national security of the United States by helping two countries that have been and remain key forces "for political stability and economic progress in the Middle East."Raytheon Co is another key contractor on the program.THAAD is a US Army system designed to shoot down short-, medium- and intermediate-range ballistic missiles with an interceptor that slams into its target.It can accept cues from Lockheed's Aegis weapons system, satellites and other external sensors, and works in tandem with the PATRIOT Advanced Capability-3 terminal air-defense missile. THAAD includes its own radar along with interceptors and communications and fire control units.US officials have said their ultimate goal is a regional shield that can be coordinated with US systems, a system similar to Washington's drive to expand missile defense to protect NATO's European territory against ballistic missiles that could be fired by Iran.THAAD is part of a layered missile shield being built to defend the United States and its friends and allies against ballistic missiles of all ranges and in all phases of flight. The system is being optimized against Iran and North Korea.The Defense Security Cooperation Agency (DSCA), which oversees foreign arms sales, formally notified lawmakers on Friday that it had approved the possible sales, which come against the backdrop of heightened tensions with Iran.Lawmakers now have 30 days to block the potential sales although such action is rare since deals are carefully vetted with lawmakers weeks before the notifications are posted.Lockheed told reporters in August that Saudi Arabia and its closest regional partners in the Gulf Cooperation Council had shown interest in the company's Terminal High-Altitude Area Defense (THAAD) weapon systems.Secretary of State Hillary Clinton met GCC officials in September and US officials said initial missile-defense sales could be announced soon.The GCC is a political and economic alliance linking Saudi Arabia, Kuwait, the United Arab Emirates, Qatar, Bahrain and Oman. Washington has been working with Gulf states on a bilateral basis, not as a group, to boost the range of radar coverage and related capabilities across the Gulf for the earliest possible defense against any missiles fired by Iran.The United States and its allies say Iran is seeking nuclear weapons capability under the cover of a civil program. Iran denies this, but has been hit with a series of international sanctions over its nuclear work.