The department's Civil Rights Division wrote last month it concluded the city  "had engaged in a pattern or practice of employment discrimination" and said the  division had authorized attorneys to go to court.

"The United States will file its complaint no later than April 20," read the  letter by Delora Kennebrew, chief of the employment litigation section.

Federal lawyers concluded that promotions tests for four ranks — engineer,  lieutenant, captain and district chief in the department's fire suppression  division — had unfairly hindered black firefighters' advancement.

To make up for that, the Justice Department wants the city to change its  promotion practices and provide "make-whole relief." That would include job  offers, back pay with interest and changes in seniority for firefighters harmed  by tests that were discriminatory, according to the letter.

The International Association of Firefighters also will be named in the suit,  Kennebrew wrote, because it negotiates with the city over terms of promotion  tests. Union President Randy Wyse did not return a message left Thursday  afternoon seeking comment.