The US budget deficit is expected to grow to US$590 billion (NZ$808 billion) in fiscal year 2016 due to slower than expected growth in revenues and higher spending for programs including Social Security and Medicare, the Congressional Budget Office (CBO) says.
The estimate, which is US$56b (NZ$76b) larger than CBO's forecast in March, shows the deficit increasing in relation to economic output for the first time since 2009.
CBO said the deficit is expected to be US$152b (NZ$208b) higher than in 2015 and will equal 3.2 percent of economic output.
The non-partisan research agency also said that debt held by the public will amount to nearly 77 percent of gross domestic product by the end of 2016, three percentage points higher than last year and its highest ratio since 1950.
The 2016 federal fiscal year ends September 30.