Revealed: Saudi Arabia Owns $117 Billion of US Debt

That makes Saudi Arabia the 13th largest foreign holder of US debt, though well behind the $1 trillion-plus owned by China and Japan each.

Unlike with most other major owners of US debt, the Treasury Department kept Saudi Arabia's precise holdings secret since the 1970s. Saudi's holdings were lumped together with that of other oil exporting nations, including Venezuela and Iraq.

But that policy ended on Monday as the Treasury Department disclosed precise holdings by specific countries that were previously grouped together. A Treasury official told CNNMoney the move was made following a review aimed at trying to provide more "comprehensive and transparent" data.

It is possible that Saudi Arabia owns even more US debt than what was revealed on Monday. That's because Saudi Arabia's central bank listed owning $587 billion of foreign reserves as of March. Typically, central banks park the majority of their foreign reserves in US Treasuries. In other words, the numbers don't really add up.

The Saudi mystery had taken on greater significance in recent months. Since the end of 2014 the Saudis have burned through more than $130 billion of foreign-exchange reserves -- most likely including US debt -- to help cope with the crash in oil prices. The Treasury Department said Saudi Arabia's US debt holdings of $116.8 billion are down from $123.6 billion in January.

Additionally, rising tensions between the US and Saudi Arabia led the kingdom to make a recent shocking threat. Sources told CNN in April that Saudi Arabia threatened to sell off American assets if Congress passed a bill that would allow 9/11 victims to sue foreign governments. A Saudi source at the time told CNNMoney that the kingdom was "serious" about this threat.

Dumping a vast sum of US Treasuries at once could cause the securities to tank, potentially destabilizing global financial markets. It could also severely hurt Saudi Arabia's own finances, leading many experts to conclude the threat was empty.