The State Department has approved the possible sale of 44 Terminal High Altitude Area Defense missile launchers to Saudi Arabia, worth up to $15 billion.

The sale is part of the $110 billion mega arms deal with Saudi Arabia that President Trump announced during his trip there in May, according to a State Department official.

The THAAD sale would further "U.S. national security and foreign policy interests and supports the long-term security of Saudi Arabia and the Gulf region in the face of Iranian and other regional threats," the official said.

The news comes one day after Saudi Arabia reportedly agreed to buy S-400 surface-to-air missiles from Russia. Reuters reported that Saudi King Salman and Russian President Vladimir Putin agreed to the sale during the king's visit to Moscow this week.

Sen. Tom Cotton, R-Ark., applauded news that the U.S. sale had been approved.

"This is just the kind of move we need to box in Iran's imperial aggression. It also will draw upon the talents and work ethic of the people of Camden, Arkansas, where key components of the THAAD system are made," Cotton said in a statement. "These patriotic Americans will once again do their part in protecting our country and the world from a reckless, brutal regime.

"This will strengthen the economic ties between us and our ally, as well as strengthen economic growth right here at home. I applaud the State Department's decision, and it comes not a moment too soon."

Friday's announcement merely means Congress has been notified of the potential sale. It won't go through until officials with Lockheed Martin, the U.S. government, and Saudi Arabia sign a contract through the Foreign Military Sales process.

The sale would cover 44 launchers, 360 interceptor missiles, 16 fire control and communications mobile station groups, and seven radars.

"THAAD's exo-atmospheric, hit-to-kill capability will add an upper-tier to Saudi Arabia's layered missile defense architecture and will support modernization of the Royal Saudi Air Defense Force (RSADF)," the Defense Security Cooperation Agency said in a statement. "Saudi Arabia will have no difficulty absorbing this equipment into its armed forces."

Critics pointed out that when Trump announced the deal in May, $24 billion of the $110 billion had already been approved by the Obama administration, going as far back as 2013.

"It's fake news," wrote Bruce Riedel on the website of the Brookings Institution.

"There is no $110 billion deal. Instead, there are a bunch of letters of interest or intent, but not contracts," wrote Reidel, director of the Brookings Intelligence Project. "Many are offers that the defense industry thinks the Saudis will be interested in someday."