WITH THE CITY'S convention-center plan at a perilous point in its passage through Congress, this is no time for silence on the part of those in this community, in and out of public office, who favor the project. Silence is powerful ammunition for those in Congress who want to kill off this community effort out of hand. Fair or unfair, this is a yardstick Congress so often uses in deciding important questions about what the city may or may not be allowed to do. Moreover, in the case of the convention center, the extent of local support does happen to be germane to the plan's merits; without strong and sustained community support, it would be a mistake to embark on this venture at all.

That is why, as we understand it, various members of the community - religious and civie leaders, top labor officials and representatives of large as well as small business - have been considering how they might demonstrate the intensity of their commitment to the convention-center project. The idea apparently is to organize a public meeting of representatives from a wide range of community groups who would explain their reasons for supporting the project, answer questions about it and generally convey their solidarity aon the matter.

The time for this effort, if it is to assist members of Congress in understanding the case for the center, and the degree of community support for it, is right away. The House meets Monday to vote on an extension of the city's long-standing borrowing authority. Approval of that measure is crucial to the center plan, not the mention the entire capital program of the city.

Naturally, the one man who should play a top role in this effort is the mayor. It's no secret that Mayor Washington supports the convention-center plan. Indeed, he has said he considers it a keystone in the economic development of the District. But the word is about that city hall is not eager to get caught up in a mass, broadly based manifestation of community supports. We hope that's not so. For any sign, however ill founded, that city hall is unwilling to take the kind of question that has troubled us all along about the convention-center debate - namely, is there the depth and breadth of support for the project that its advocates would like to believe, and that will be essential to see it through to completion? There can be no question about the backing of the business community, and of organized labor and of church groups and important political leaders such as Delegate Walter E. Fauntroy and msot members of the City Council. Almost the only missing ingredient, in fact, is a strong lead from city hall. We hope that the mayor will provide that lead this weekend in an effort to demonstrate to Congress the solidarity of the community on the convention-center question.He has done it before in times of emergency - and it is not too much to say that this is close to being one of those times.