With prominent black Republicans on the dais, the National Business League yesterday announced its opposition to Reagan administration plans to eliminate the Small Business Administration and cut urban development action grants.

Among black businessmen who participated were league president Arthur E. Teele Jr., the first head of the Urban Mass Transportation Administration under President Reagan, and C.J. Patterson, a Republican from California who has supported Reagan since he was governor of that state.

"The time has come for both Congress and the administration to take a close look at the proposed budget in terms of what will happen to the black American struggling to enter the mainstream . . . ," Teele said. "The administration's plan to eliminate SBA locks out the minority entrepreneur. The failure to hold the Defense Department accountable, in terms of sharing a multibillion-dollar budget, is equivalent to putting a padlock on the entry to the marketplace for minority-owned business."

Patterson said black businessmen agree with their white counterparts that reducing the budget deficit must be a priority for the government, but said the administration needs to foster the growth of successful black businesses.

"The deficit ought to be addressed," Patterson said, "but not at the expense of minority business. Why do minority businesses have to carry the brunt of the load all the time, even on the deficit?"

Similarly, Teele said programs supported by black business should have to share in the cuts that social programs are expected to undergo. But, he said, "it's a matter of emphasis, and black business should be important to this administration. If black businesses succeed, they hire blacks; there is less pressure on social spending."

The league recommended that the president instruct the Defense Department to award more contracts to minority-owned businesses and that the President's Commission on Private Sector Initiatives study ways to help them.

In addition, the league said Congress should change the tax system to "stimulate contributions and investment in small and minority-owned businesses." It also called on Congress to enact tax incentives enabling cities to set up enterprise zones to stimulate downtown redevelopment.

Teele said that, although the timing of the proposal to eliminate the SBA "couldn't be worse," he would recommend transferring it to the Housing and Urban Development Department, rather than the Commerce Department, if it is abolished as a separate agency. He said HUD has experience dealing with urban areas, while Commerce has an international-trade focus and "lacks sensitivity to minority businesses." Commerce, however, does have a Minority Business Development Agency.

The league also asked Reagan to ensure that the Pentagon's Office of Small and Disadvantaged Business Utilization is not diminished or abolished when the budget is cut.