Saudi Arabia will purchase a $15 billion missile system from the American defense giant Lockheed Martin, a US State Department spokesperson told Reuters on Wednesday.

A last-minute push by Washington to close the deal included a phone call between US President Donald Trump and Saudi King Salman, according to the news wire.

The parties signed off on the purchase of 44 Terminal High Altitude Area Defense (THAAD) launchers, missiles, and related equipment on Monday.

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The deal, which has been in the works since December 2016, appeared at risk, following pressure from Congress to downgrade US ties with Saudi Arabia, after the CIA concluded that Crown Prince Mohammad Bin Salman had ordered the brutal murder of US-based Saudi journalist Jamal Khashoggi, in the Saudi consulate in Istanbul in October.

But Trump stood by Riyadh nonetheless, suggesting, in defense of his policy, that Israel would face major regional difficulties in the Middle East were it not for the stabilizing presence of Riyadh.

“If you look at Israel, Israel would be in big trouble without Saudi Arabia,” Trump said Monday. “So what does that mean, Israel is going to leave? You want Israel to leave? We have a very strong ally in Saudi Arabia.”