The deficit will reach $960 billion for the 2019 fiscal year, which ends Sept. 30, and $1 trillion for the 2020 fiscal year, the Congressional Budget Office said in updated forecasts released on Wednesday. Previously, it had projected an $896 billion deficit for 2019 and $892 billion for 2020. Those numbers would be even higher, if not for lower-than-expected interest rates, which are reducing the cost of servicing the national debt.

Rising deficit projections are the result of sluggish growth in federal revenue after Mr. Trump’s 2017 tax cuts went into effect, and several bipartisan agreements to raise military and nondefense domestic discretionary spending, which Mr. Trump signed into law.

Typically, the budget deficit shrinks when unemployment is low. Mr. Trump’s administration has defied that trend.