About 400 District government workers from various public employe unions staged a show of solidarity and force yesterday in an early-morning demonstration at the District Building, protesting Mayor Marion Barry's planned 5 percent pay raise for city workers.

Barry and the unions have been at odds over the pay raise issue since the mayor proposed the 5 percent increase, less than the 9.1 percent federal workers will receive.

The unions are demanding that the mayor bargain with them collectively for wages, and union leaders have threatened to challenge in court Barry's authority to decide unilaterally how much of an increase workers will get this year.

Yesterday morning's demonstration was the first since the unions banded together in a coalition, and the first since union leaders began publicly acknowledging the possibility of a strike over the wage issue.

"We haven't gotten to the point where we're calling people off their jobs yet" to join in demonstrations, said Robert E. Peterson, president of the Greater Washington Central Labor Council, who is acting as spokesman for the labor coalition. "It was mainly just a brief rally to say once again to them that we're all unified."