WASHINGTON — President Bush said today that “it’s clear our economy has slowed” and tried to reassure an anxious public that the long-term outlook is good.

“Losing a job is painful and I know Americans are concerned about our economy. So am I,” Mr. Bush said during a hastily arranged White House appearance on the heels of a gloomy government economic report.

“I know this is a difficult time for our economy,” he said. “But we recognized the problem early and we provided the economy with a booster shot.”

Congress passed and Mr. Bush signed a stimulus package that will send tax rebates to many families and businesses. But some fear it will come too late — or that people will use the money to save or pay off debt, rather than go on a spending spree that will boost the economy.

Mr. Bush urged people to do the latter. “When the money reaches the American people, we expect it to boost consumer spending,” he said.

Earlier, the president’s top economic adviser said that the nation’s economic growth could dip into negative territory for the current quarter. That tracks with the assessments of many outside experts but is the most pessimistic word to come so far from the White House.

“We don’t really know whether it will be negative or not,” Edward Lazear, chairman of the White House Council of Economic Advisers, told reporters at the White House. “We have definitely downgraded our forecast for this quarter.”

The flurry of activity came as the White House was eager to put a good face on the economic picture, clouded by the release earlier today of a report showing the economy lost 63,000 jobs last month, the most in five years.