Black Caucus convenes to talk politics and discuss priorities. MARSHALL SETS TONE

Black people are living in an age when they can realize the rights they have been seeking, says United States Supreme Court Justice Thurgood Marshall. ``As long as I can breathe and aspire for justice, I intend to serve,'' he told the cheering banquet audience.

This moment was an unlisted feature of the 18th annual Congressional Black Caucus Legislative Weekend, sponsored by the CBC Foundation. It was a tribute to Justice Marshall, the first black to serve on the Supreme Court, who was chief counsel for the National Association for the Advancement of Colored People during the 1960s, when the NAACP pursued and won many civil rights cases before the Supreme Court.

Marshall, who is 80 years old, declared, ``I was appointed to serve for life. I intend to serve as long as I aspire for justice, as long as I take a human breath.'' He set the tone for a series of 64 workshops and public sessions.

Although only 23 blacks serve in Congress, they drew more than 15,000 people to Washington, including many state and local black elected officials, to discuss a proposed black agenda and possibly to hear both presidential candidates speak.

The congressmen, all Democrats, acknowledge black progress in the past 18 years. But participants in weekend activities emphasized that they expected changes from the president who succeeds Ronald Reagan.

Gov. Michael Dukakis of Massachusetts, the Democratic candidate, will address the closing event, a $300-a-plate dinner, Saturday night. He is to appear with Jesse Jackson, his chief opponent for the party's nomination. The caucus will honor the Rev. Mr. Jackson, the first black to race to the wire for a major party's presidential candidacy.

Vice-President George Bush, the Republican candidate, was not invited to address a caucus event. But the local chapter of the National Black Republican Council has invited him to speak tonight at its fourth annual scholarship dinner.

During his address Wednesday evening Justice Marshall said ``the struggle is not over. We've got a long way to go. Tell the other side to look out. We're still here. Don't give up!'' Activities have been planned to emphasize key policies and goals stressed by black congressmen as musts:

The election of more blacks.

More jobs for blacks and higher minimum wages for all Americans. Establishment of more black businesses with more government contracts.

More preschools for minority children, quality public schools, more access to college training, especially for the poor.

Ways to reduce the influence of crime and drug dealing on black youth.

For the family, better and affordable housing, attention to improving health, stable black communities.

Participants expressed despair over gang warfare, said to be tied to drug abuse, that makes homicide the greatest cause of death among young black males between the ages of 16 and 24.