Here are the 17 countries that hold the most US debt

US sovereign debt is one of the safest assets in finance.

But that safety was called into question this month by US presidential candidate Donald Trump, who said the US could negotiate with creditors and wouldn't need to pay the whole $13 trillion back.

The US Treasury published more detailed data on who owns that debt for the first time since the 1970s, giving a breakdown of Saudi Arabia's holding of the debt.

The report gave details on specific countries that previously been lumped together such as "oil exporting nations" and "Caribbean banking centers," according to the Associated Press.

The Treasury showed that Saudi Arabia held $116.8 billion of US debt in March, down 2.5% from February.

Here's how the rest of the world's US debt holders measure up, as of March this year: