Unemployment rose slightly last month but the number of Americans who found work in March continued to rise rapidly, the government reported yesterday.

Labor Department analysts said the increase in the jobless rate from 6.1 per cent in February to 6.2 per cent in March was so small that it was insignificant. Most of the overall increase was concentrated among black women and black teenagers.

The unemployment pictures has gotten better much more rapidly than administration officials had hoped, even as late as December. In Carter's first full month in office in February 1977, joblessness stood at 7.6 per cent.

Even though the improvement in the unemployment rate has been marked and rapid, at 6.2 per cent the rate remains very high, especially so late into an economic recovery.

White House press secretary Jody POwell said yesterday that the administration is "disappointed" with the rise in black unemployment," but that the President was not disturbed by the small insignificant rise in the overall rate.

But recent sharp increases in wholesale and retail prices, coupled with warnings that inflation could get worse in the months ahead, has pushed the unemployment question to the back burner as the administration's top economic officials put the finishing touches on a Presidential anti-inflation policy.

President Carter is expected to unveil his anti-inflation policy on Tuesday in a speech to a meeting of the American Society of Newspaper editors here.

The centerpiece of his proposal is expected to be a 5.5 percent ceiling on pay increases for federal employes. The President wants a gradual deceleration in inflation and wants business and labor to co-operate in lessening wage and price demands enough to knock half a percentage point off the "underlying" inflation rate.

The Senate Budget Committee, which is now working on the 1979 federal budget , has proposed a 5 percent cap on federal pay increases.

Barry P Bosworth, director of the White House's Council on Wage and Price Stability, said in a report Thursday that inflation seems to be "hopelessly stuck" between 6 an 7 percent and said new efforts were needed to keep that rate from accelerating.

Nevertheless, the last two inflation reports - one on a wholesale, one on retail prices - show a slight moderation in inflation, although the pace of price increases continues to be high.

Except for the slight increase in the overall jobless rate and a rise in unemployment for black women from 10.1 percent to 11.4 percent, nearly all the rest of the jobs report was encouraging.

According to a survey of households, from which the unemployment rate is derived, 260,000 persons found jobs in March. Because 321,000 Americans joined the labor force, however, the number of unemployed rose by 58,000.

Another survey of employer payrolls, which is considered less inclusive but more accurate on a month-to month basis, showed a gain of 445,000 jobs in March.

Julius Shiskin, commissioner of labor statistics, also reported a sharp increase in hours worked by production workers. "The large rise in hours was widespread, probably marking the end of the especially bad weather during the winiter," Shiskin testified before the Joint Economic Committee.

over the last year the number of jobless has declined by more than one million and the number of persons finding jobs has risen by more than 3.5 million, according to the Labor Department's monthly survey of 56,000 households. In March 93.3 million persons had jobs and 6.1 million were unemployed.

Shiskin said the coal strike had little impact on the jobless picture in March noting that despite the strike 263,000 persons found employment. Some administrations officials, especially Energy Secretary James Schlesinger, warned of dire employment consequences of the coal strike.

in fact, the 445,000 increase in jobs recorded by the payroll survey was one of the largest in history, Shiskin said.

The unemployment rate is the percentage of the labor force that is out of work and actively seeking a job. The Labor Department said that the number of discouraged workers - those who are jobless but not seeking work - averaged 903-000 in the first three months of 1978, down from 969,000 in the final months of 1977.