The economy performed slightly better in the first three months of the year than the government originally estimated, the Department of Commerce reported yesterday.

The department said the gross national product, the value of all goods and services produced by American citizens, grew not at all in the first quarter. In its previous estimate, the Commerce Department said total output declined 0.4 percent.

The gross national product, after adjustment for inflation, is the broadest measure of economic performance economists possess.

Analysts have predicted that the economy could grow at an annual rate of 8 to 10 percent before settling into a more moderate 4 to 4.5 percent rate in the final six months of the year.

The department also reported that profits fell 2.5 percent after taxes, compared with an initial estimate that profits dropped 2 percent in the first quarter. In the final three months of 1977 corporate profits rose 1.4 percent.

Corporate profits ran at a seasonally adjusted annual rate of $102.4 billion in the first quarter.

In another development, the Business Roundtable, an organization of chief executives of the largest American corporations, pledged support for President Carter's program to reduce the rate of inflation by a half percentage point this year, but warned that private efforts to reduce inflation will come to naught unless the federal government adopts sound "fiscal, monetary and regulatory policies."

Meanwhile, Office of Management and Budget director James McIntyre told reporters yesterday that President Carter will not be able to balance the budget in 1981 after all. Administration officials have been implying that for months, but McIntyres statement was the first formal deferral of the goal.