Saudi Arabia, US take a significant step toward closing $15 billion deal for Lockheed Martin's THAAD missile defense system

Saudi Arabia has signed a letter of offer and acceptance with the United States for Lockheed Martin's THAAD missile system, a significant step forward in the $15 billion deal, a State Department spokesperson confirmed to CNBC.

Saudi officials, alongside their U.S. counterparts, signed the crucial government-to-government agreement earlier this week, paving the way for the massive sale of 44 THAAD launchers, missiles and related equipment.

Manufactured by Lockheed Martin, the Pentagon's top weapons supplier, THAAD, or terminal high altitude area defense, is regarded as America's crown jewel in missile defense systems.