The nation's civilian unemployment rate dipped to 7.3 percent in February, despite the continued erosion of jobs in manufacturing and worsening job picture for blacks, the Labor Department reported.

The February unemployment rate fell a slight 0.1 percentage point below the January level, as the number of people with jobs increased by 294,000. In manufacturing, however, the number of jobs declined by 82,000 during the month.

The number of people with jobs rose to 106.7 million in February and the number of unemployed persons was 8.4 million, little changed from the previous month. The overall jobless rate, including the armed forces, fell to 7.2 percent from 7.3 percent in January.

The unemployment gap between blacks and whites widened last month, but it was "difficult to judge whether the February figures mean a further widening in the months to come of the already large gap in black/white jobless rates," said Janet L. Norwood, commissioner of the Bureau of Labor Statistics.

The unemployment rate last month for whites dropped from 6.4 percent to 6.2 percent, compared with an increase from 14.9 percent to 16.3 percent for blacks.

The White House reveled in the increase in new jobs, which produced the first decline in the unemployment rate since November.

"We have seen a number of positive economic indicators in recent weeks, but none is as reassuring as a drop in unemployment," said White House spokesman Larry Speakes. "More and more people are receiving paychecks. And consumer confidence remains strong. These are the ingredients for a promising economic future."

However, Norwood told the Joint Economic Committee yesterday that "both the level and the rate of unemployment have changed little since last May, following steady declines throughout 1983 and the first half of 1984."

Most of the job gains have been in services, retail trade, finance, insurance and real estate, while "each of the industries in the goods-producing sector declined in February," Norwood said.

An index measuring how widespread job gains were, particularly in manufacturing industries, dropped to 47 percent, indicating that less than half of the 185 industries surveyed had job gains. That was the lowest level for that index in five months.

Some labor market analysts blame the surge in imports for the loss of many jobs in the manufacturing industry, which must compete with foreign goods in the U.S. market as well as in markets abroad.

The average workweek of production workers on private nonagricultural payrolls declined 0.2 hour to 35.0 hours and factory hours also dropped 0.6 hour to 40.0 hours.

Norwood said part of the problem for blacks was that they tend to work in areas where jobs are declining, such as in manufacturing centers of the Midwest and Northeast.

The highest level of black unemployment during the last recession was reached in December 1982, when the rate was 20.9 percent, according to Deborah Klein, a Labor Department economist. Since then, the rate for blacks has fluctuated between 15 percent and 16 percent and reached 14.9 percent in January, Klein said.

The white unemployment rate peaked at 9.6 percent in December 1982 and reached its low point at 6.1 percent last November. The rate for whites has fluctuated between 6.1 percent and 6.5 percent since last May, Klein said.

The Full Employment Action Council reported yesterday that blacks are two to three times as likely to be unemployed over the long term than are whites because of blacks' "higher probability of becoming unemployed in the first place."

The jobless rate for men last month was 6.3 percent, unchanged from the previous month, and the rate for women was 6.7 percent, down from 6.8 percent, the Labor Department said. The rate for teen-agers was 18.4 percent, down from 18.9 percent. The jobless rate for Hispanics declined from 10.6 percent to 9.7 percent.