And then there is the possibility of more new spending. President Trump’s pledge of up to $12 billion in emergency relief for farmers hurt by the trade war is prompting new demands for relief for manufacturers, fishermen and others being hit by retaliatory tariffs from American trading partners — all of which would require more government spending.

As the tax bill was debated last year, the Trump administration argued that losses from the cuts would be offset by increased economic growth. Companies would use money that had previously gone to taxes, the argument went, to invest in their businesses and workers, giving the government a smaller slice — but out of a bigger pie.

But the drop in tax payments has come as the American economy is already the healthiest it has been since the crisis, raising questions about whether the deficit could balloon further if growth begins to slow. The Commerce Department on Friday will announce its first estimate of gross domestic product in the second quarter, and forecasters anticipate it could reach 5 percent, the highest rate since 2014. Analysts, however, expect growth to slow in the second half of the year, as interest rates continue to rise and trade tensions weigh on the economy.

There was some encouraging news on the front Wednesday: After months of escalation, Europe and the United States agreed to find a way to reduce tariffs and other barriers, although how that could weigh on growth remains to be seen.

“It is unwise to count on sustained revenues from growth that could easily prove to be a temporary sugar-high,” said Maya MacGuineas, president of the nonpartisan Committee for a Responsible Federal Budget in Washington, “particularly when it ignores the very real threat that the economy slows and we enter a downturn in a very vulnerable fiscal position.”

But administration officials are dismissing such concerns, arguing that they still expect economic activity to remain strong.

“We are very much looking forward to the second quarter G.D.P. numbers, which we anticipate will keep us on track to a four-quarter growth rate over 3 percent for the first time in 13 years,” said Kevin A. Hassett, the chairman of the White House Council of Economic Advisers. “That’s a growth rate nobody thought was possible and we are glad to see the naysayers will be proved wrong.”