The majority of the 19 hijackers involved in 9/11 were from Saudi Arabia, with the remaining four from Lebanon, the UAE and Egypt.
Barack Obama introduced a law during the last year of his presidency which allowed victims to sue the Saudi government for its role in the attack.
The law, named the Justice Against Sponsors of Terrorism Act, held governments responsible for the actions of their citizens against US nationals.
GettyDonald Trump (L) and Mohammed bin Salman, Deputy Crown Prince
Just under 3,000 people died in the 2001 atrocity, which saw hijackers crash planes into the North and South Twin Towers in New York and the Pentagon in Virginia.
Passengers managed to over-power hijackers on a fourth plane, which then crashed in the Pennsylvania countryside.
The Saudi Energy Minister Khalid al-Falih, who is also head of the petroleum company Aramco, said his government was “hot happy” about the passage of the Act, which is also known as Jasta.
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U.S. President Trump and German Chancellor Merkel hold a joint news conference in Washington