WASHINGTON — President Trump on Tuesday evening threatened to derail months of bipartisan work in Congress to deliver $900 billion in coronavirus relief to a country battered by the pandemic, demanding sweeping changes and cuts to a bill he called a “disgrace.”

The president, who has been preoccupied with the baseless claim that the election was stolen from him, seized on congressional leaders’ decision to pass the relief bill by combining it with a broader spending plan to fund government operations and the military, portraying the other spending items as “wasteful and unnecessary.”

“It’s called the Covid relief bill, but it has almost nothing to do with Covid,” Mr. Trump said in a video posted on Twitter.