U.S. Attorney Earl J. Silbert announced his resignation yesterday, setting off speculation and initial maneuvers among politicians and lawyers concerned with the choice of a successor.

In letters to President Carter and Attorney General Griffin B. Bell, Silbert, 43, said he will leave the office on June 29, after 5.1/2 years as U.S. attorney. He will become a partner in the Washington law firm of Schwalb, Donnenfeld and Bray - to which the name Silbert will be added.

A knowledgeable White House source said yesterday that the Carter administration has not yet begun any serious consideration of candidates to fill the vacancy created by Silbert's departure.

The most frequently mentioned candidate for the job is Togo West Jr., 36, now a special assistant to Defense Secretary Harold Brown. West, a 1968 graduate of the Howard University Law School, is a native of Winston-Salem, N.C. A close friend of City Council Chairman Arrington Dixon, West has also worked for the Washington law firm of Covington and Burling, served as associate deputy attorney general in the Justice Department and was general counsel for the Navy. West could not be reached for comment yesterday.

About a year ago, the White House conducted a low-key search for a local black attorney to take over the U.S. attorney's job, one of the few appointments an incumbent president can make in the District.

Candidates mentioned then - and considered possible choices now - were West, Vincent Cohen, a partner with the Hogan and Hartson law firm, Robert P. Watkins, a partner at Williams and Connolly and Wesley S. Williams Jr., a partner in Covington and Burling.

The increasingly strong lobby of women lawyers in the District may lend its support to Margaret A. McKenna, deputy counsel to President Carter, a source said.

Other names included in discussions among local lawyers and politicians of possible candidates are James Dyke, special assistant to Vice President Mondale, Frederick B. Abramson, a partner in the Washington law firm of Sachs, Greenebaum and Tayler, former D.C. Corporation Counsel John R. Risher Jr., now a partner at Arent, Fox, Kintner, Plotkin and Kahn and former Watergate special prosecutor Charles Ruff, now an associate deputy attorney general at the Justice Department.

In his letter to President Carter, Silbert wrote at length about his opposition to a proposal that the bulk of the responsibility of the U.S. Attorney's Office be transferred to a local prosecutor. That proposal, still in the planning stages, is expected to complicate the search for a new federal prosecutor.

The U.S. Attorney's Office in Washington, unlike any other federal prosecutor's office in the country, handles virtually all of the city's criminal cases. The new U.S. attorney, one source said, "will preside over the dismantling of the office," now the largest in the country.

One source said yesterday that it was understood that Silbert had strongly recommended his principal assistant, Car S. Rauh, for the U.S. attorney's job. Silbert refused to comment yesterday on any recommendations he may have made to the Justice Department in terms of a successor.

Silbert's term as U.S. attorney expires in October. In his letter to Carter, delivered late yesterday, Silbert acknowledged that the timing of his departure was affected by new restrictions in the Ethics in Government Act, of 1978, which take effect July 1. Those rules would have set various limits on Silbert's private law practice after he left the government.