The federal government's IOU has now more than doubled in less than a decade, from $19.95 trillion when US President Donald Trump was sworn in for the first time in January 2017. The latest milestone comes as Washington faces mounting pressure to balance defence priorities, social spending, economic growth and fiscal sustainability. Key points and original sources are listed below.

• The federal government's IOU has now more than doubled in less than a decade, from $19.95 trillion when US President Donald Trump was sworn in for the first time in January 2017.S1

• The latest milestone comes as Washington faces mounting pressure to balance defence priorities, social spending, economic growth and fiscal sustainability.S2

• The US gross national debt surpassed $40 trillion for the first time, Treasury data showed on Wednesday, exceeding earlier forecasts as borrowing, interest costs and long-term obligations rose. Total public debt reached $40.05 trillion on Tuesday, above a Cong...S3

• The record milestone underscores the mounting cost of government borrowing as Washington faces growing spending demands and rising interest payments.S4