The U.S. budget deficit likely will break the $1 trillion barrier in 2020, the first time that has happened since 2012, according to Congressional Budget Office estimates released Tuesday.

After passing that mark this year, the deficit is expected to average $1.3 trillion between 2021-30, rising from 4.6% of GDP to 5.4% over the period. That's well above the long-term average since around the end of World War II. The deficit since then has not topped 4% of GDP for more than five consecutive years, averaging just 1.5% over the period.

As part of a spending pattern that the CBO deemed unsustainable, the national debt is expected to hit $31.4 trillion by 2030.

Tuesday's projections reflect a slight increase from the estimates presented in August 2019.

"A trillion-dollar deficit is not a milestone to be proud of, nor one to brush aside. Over half of the deficit is due to the choice of policymakers to borrow to fund recent tax cuts and spending increases," Maya MacGuineas, president of the Committee for a Responsible Federal Budget, said in a statement. "CBO's report confirms that not only are we in uncharted waters, but that we are also leaving future generations with an incredible burden.

In addition to the debt and deficit outlook, the CBO expects the economy to grow at a 2.2% pace in 2020. The office also estimated that real exports will rebound this year, driven mostly by a push in aircraft exports once the Boeing 737 MAX deliveries resume.

Economic growth also will come based on continued consumer strength and a rebound in business fixed investment, according to the CBO.