Mattis today affirmed the importance of the U.S. -Saudi Arabia defense relationship in a meeting at the Pentagon with Saudi Defense Minister Crown Prince Mohammed bin Salman, chief Pentagon spokesperson Dana W. White said. "Saudi Arabia is a very wealthy nation, and they're going to give the United States some of that wealth, hopefully in the form of jobs, in the form of the purchase of the finest military equipment anywhere in the world", Trump said.
"This proposed sale will support US foreign policy and national security objectives by improving the security of a friendly country", the US Defense Department said in a statement.
Rights groups have repeatedly condemned the U.S. and UK's continued arms sales to Saudi Arabia in light of the Kingdom's human rights violations in Yemen, many of which are thought to be war crimes.
According to a Human Rights Watch report, munitions supplied by Raytheon - the company which will supply Saudi with the anti-missile systems under the new deal - have been traced back to Saudi-led air strikes against innocent civilians.
"But this has not deterred the USA, UK, and other states, including France, Spain and Italy, from continuing transfers of billions of dollars' worth of such arms", it added.
According to the SIPRI report, which was released last week, Saudi Arabia increased its arms purchases by 225 percent over the past five years, importing 98 percent of its weapons from the U.S. and European Union countries.
Mattis said he believes Saudi Arabia is "part of the solution".
The United States and Britain are both signatories to the treaty, which regulates the worldwide trade of conventional arms for the goal of "contributing to global and regional peace, security and stability" and "reducing human suffering".
Critics say Saudi aid in the shadow of the coalition's blockade on Yemen exclusively puts the response to the humanitarian crisis in the hands of an active party in the conflict and does not reach Houthi-controlled territory.
During Senate debate before the vote, some backers called the three-year-long conflict in Yemen a humanitarian catastrophe, which they blamed on the Saudis.
Prior to the meeting, the former said that Saudi Arabia was a "part of the solution" in Yemen, in the midst of a civil war in the country, which, according to experts, has killed thousands of civilians in airstrikes, initiated by Riyadh.
An attack in August on a residential neighbourhood in Sanaa, the rebel-controlled capital, killed 16 civilians, majority children.
The United States provides refuelling and intelligence support to the Saudi-led coalition.