The National Association for the Advancement of Colored People (NAACP) will announce today that it is filing suit against the independent NAACP Legal Defense and Educational Fund, Inc., to force the fund to stop using the NAACP initials in its name.

The NAACP has called a press conference for 10:30 this morning to announce the suit, which represents a bitter split within the ranks of the celebrated civil rights organizations. If pursued in court, the issue will pit former allies against one another. The NAACP has retained former senator Edward Brooke as its lawyer, reportedly for a substantial fee, while the legal defense fund will be represented at no cost by Vernon Jordan, former director of the National Urban League, and two other attorneys.

In a formal statement released last night, the legal defense fund said it was "saddened" by the legal move. "At a time when civil rights groups should be working together, the lawsuit is a disgraceful waste of resources," said William T. Coleman Jr., the former secretary of transportation, who is chairman of the legal defense fund's board.

Informed that word of the lawsuit had leaked out, the NAACP last night also released a statement on the background of the dispute. It said the NAACP "holds a trademark" on the initials and considered the legal defense fund's refusal to drop them as a "grave" matter.

The legal defense fund was established in 1939 to create a tax-exempt arm of the NAACP that could raise its own funds and pursue legal and educational efforts to improve the lot of the nation's blacks. Until 1957 the two organizations had overlapping boards of directors, but in that year the Internal Revenue Service ruled that they had to be completely separate.

They continued to work cooperatively, with occasional disputes, until the late 1970s, when the new leadership of the NAACP which succeeded Roy Wilkins, the longtime executive director of the organization, made an issue of the initials.

The NAACP statement released last night implied that the dispute involved pride. It complained that the public did not realize that the legal defense fund and the NAACP were separate organizations, and it blamed Jack Greenberg, longtime director of the fund, for falsely denying credit to the NAACP for its role in winning the 1954 Brown vs. Board of Education case that led to desegregation of the nation's schools.

The NAACP statement also criticized Greenberg for holding a ceremony commemorating the Brown decision and not inviting any black people to it. Other knowledgeable sources close to both sides said Margaret Bush Wilson, chairman of the NAACP's board, was the principal personality pushing for the lawsuit.

The split between the NAACP and the legal defense fund has upset many civil rights activists, several sources said last night. "It's a tragedy," said one former member of the NAACP board. "The NAACP is jealous of the legal defense fund," the source added. "It's incredible that people would put personal pride ahead of the cause."

Another knowledgeable source said money might be an issue. The defense fund has been a successful fund-raiser and currently has a $6 million budget, just a little less than the entire NAACP, which has hundreds of thousands of members.

The legal defense fund last night released a copy of the 1939 NAACP board meeting which decided to set up the fund. According to the minutes, then-directors of the organization approved a resolution allowing the fund to use the initials.

In 1979, the NAACP's national convention adopted a resolution calling on the fund to stop using the initials.