Former special Watergate prosecutor Charles F.C. Ruff is almost certain to be nominated as the next U.S. attorney for the District of Columbia instead of Togo D. West Jr., the unanimous choice of the city's elected and Democratic party leaders, knowledgeable sources said yesterday.

West, a special assistant to the secretary of Defense, had formally been nominated for the prized post by Del. Walter E. Fauntroy, the city's only representative in Congress, and endorsed by Mayor Marion Barry, City Council Chairman Arrington Dixon and the leadership of the D.C. Democratic party.

The local political leaders had hoped to use the united front endorsement to set a precedent in helping to choose local judicial appointees, and to assure that the next person to hold the job in a city 70 percent black would himself be black, as is West.

The sources said that West's selection to head the office, which prosecutes U.S. and local criminal cases here, has been opposed in large part because West, unlike Ruff, has only limited trial experience.

Moreover, the sources said, Ruff has received strong support from outgoing Attorney General Griffin B. Bell and incoming Attorney General Benjamin R. Civiletti. Ruff currently is Civiletti's chief of staff.

"My understanding is it is likely to be Ruff and it's just a matter of time [before it is announced]," one well-placed administration source said yesterday. "There's not much that can be done to avoid it. It's more strong support for Ruff than it is rejecting of West."

James Dyke, the White House aide principally responsible for District of Columbia affairs, said yesterday, 'As far as I know, a decision has not been made."

West declined to comment. Ruff, expected to become acting deputy U.S. Attorney General on Thursday when Civiletti takes over as Attorney General, said he has not been informed of any decision to fill the post.

A spokesman for the justice department also declined to discuss any pending appointment. The spokesman did say, however, that Bell had recommended one or more candidates for the post.

Local politicians have been jousting with White House officials over the appointment for the last several months.

In most jurisdictions, the choice of a U.S. attorney is heavily influenced by recommendations made by the state's senior U.S. senator and by leaders of the state party in power in the White House.

The District of Columbia has no senators so Fauntroy, in a July 10 letter to Bell, tried to assume that role by formally nominating West.

A month earlier, West had been endorsed for the position in a letter to the White House signed by Barry, Dixon, Fauntroy and the four top officials of the D.C. Democratic Party -- Chairman Robert B. Washington Jr., Vice Chairman Barbara Clark, National Committeeman John Hechinger and National Committeewoman Sharon Pratt Dixon.

Some sources were critical yesterday of the city leaders' decision to unite behind a single candidate rather than several, leaving the White House, they said, with no choice but to go elsewhere once West's qualifications for the post were questioned.

On the other hand, the Carter administration has asserted often in the past that it is in favor of increased home rule for the city. Deciding to go against the recommendation of the city leadership could be just as embarassing to it politically as the failure to get West chosen would be to the city's leaders, the sources said.

Ruff, who is confined to a wheelchair as a result of polio, is 39 and a graduate of Columbia University Law School. West, 36, is an honors graduate of Howard University School of Law.