Weeks before the controversial suicide barriers on the Duke Ellington Bridge were set to come down, the U.S. Congress has quietly derailed the project, ordering the District to justify the action and limiting funding until the city has made its case.

The congressional action, in the form of an amendment to the emergency supplemental appropriations bill signed May 25, was the result of intensive lobbying by supporters of the barriers. Since its passage, the measure has drawn an outpouring of criticism from barrier opponents, who call it an unnecessary intrusion into city affairs.

"Here you've got a local process that's been set up . . . only to have it undermined by the Congress of the United States. It's almost unbelievable," said Dick Clark, intergovernmental liaison for the District, who said he was unaware of the measure.

The D.C. Department of Public Works had been poised to remove the eight-foot barriers this summer as part of a $10 million renovation of the span over Rock Creek Park. To compensate, the District had planned to raise the handrails six inches, to roughly four feet above the sidewalk.

The barriers, installed in 1986, have sparked a whirl of debate and several shifts in the city's stance. In 1987, a mediator appointed by the mayor declared that the barriers constituted a suicide deterrent and should remain. Last summer, Mayor Marion Barry ordered the fences removed.

Lawyers for the Committee for Public Safety at the Duke Ellington Memorial Bridge, a group of local physicians and mental health groups in favor of the barriers, lobbied members of the House and Senate to have the amendment added.

"It's federal money that will be spent . . . to bring them down," said Benjamin H. Read, a former undersecretary in the Carter administration whose 24-year-old daughter committed suicide at the bridge in 1979. "It's a perfectly legitimate federal government interest."

"Is life or death in D.C. only a local problem?" asked Myles G. Glasgow, a vocal barrier supporter from Adams-Morgan. "It might be a congressman's son or daughter who jumps off the bridge."

The District received $172,000 in 1986 to have the wrought-iron fences put up and will have to reimburse the federal government if it removes them.

The amendment was sponsored by Sen. Brock Adams (D-Wash.) and in the House by Rep. Julian Dixon (D-Calif.).

In the six years before the suicide barriers were installed, 24 people jumped to their deaths from the bridge. In the four years since, there have been two suicides from the 150-foot-high span.

"I think what we've done is deter two to three suicides a year," said Glasgow. "No one said that {the fences} were 100 percent effective."

But fence opponents say the statistics do not bear that out, that the number of suicides yearly has not changed significantly.

The figures "are not only similar, they are identical," said James W. Morrison, vice president of the Kalorama Citizens Association, a barrier opponent. "What is the federal government doing telling the city how to fight the suicide problem?"