A fight has broken out between a mainstream Democratic leadership group and two-time Democratic presidential hopeful Jesse Jackson who accuses the group of snubbing him in a way that could be costly to the party in the 1992 elections.

The dispute was touched off when the moderate to conservative Democratic Leadership Council (DLC) slighted the liberal black activist by failing to invite him to speak at next month's convention in Cleveland.That gathering of party members from all 50 states will be the largest conclave outside of the party's national presidential nominating convention next year in New York.

This year's event takes on importance since it will be a showcase for prospective Democratic presidential hopefuls.

Jackson, who plans to decide this fall whether to make a third try for the nomination, told Reuters in his first comment on the slight that "clearly if we (the party) are to win, we must be committed to dialogue, establish consensus and expand our party."

He said "obviously it (the snub) was an intentional plan to stop dialogue and stop expansion" and suggested that the slight could alienate his black supporters.

The DLC was formed in 1985 after the devastating defeat of Democratic presidential candidate Walter Mondale, a liberal, by former president Ronald Reagan in an effort to shift the party rightward toward the political center.

Jackson, who attracted 7 million primary votes by coming in second to Michael Dukakis in the 1988 race for the nomination, spoke at the DLC's last two conventions, including the New Orleans event in 1990 attended by over 900 people.

"I am No. 1 or No. 2 for the nomination of our party," Jackson said in an interview. "I got 7 million votes in 1988 and no one who will be there ever got 7 million votes. We have expanded the Democratic Party. I registered more voters in the 1980s than any other Democrat, and the critical issues that we raise - reinvest in America, rebuild our country, fight a war on drugs - those critical issues remain the dominant issues of this day."

Jackson, who has sounded more and more like a candidate lately, added that the DLC has a right to decide who to invite to speak.

"They have a right to define themselves," Jackson added. "I accept that. And they have defined themselves in a way so the people who voted for me are not welcome. That's their right."

Other analysts said that party chances in 1992 against a highly popular President Bush could be seriously hurt if blacks, the core of Jackson's support, do not fully support a candidate not strongly backed by Jackson.

A DLC official said the organization invited neither Jackson nor former Sen. George McGovern, the 1972 presidential candidate toying with running again in 1992, to speak.

While the specific reason was unclear, one explanation was offered by the group's executive director, Al From, who reportedly said Jackson and McGovern represented the "old-style politics."

It was not racial, however, since other blacks will attend and speak, including Democratic Party Chairman Ron Brown, Assistant House Democratic Leader William Gray and Virginia Gov. Douglas Wilder, exploring a run for the White House.

A DLC spokewoman said Jackson was invited to attend - not deliver a speech - because there were so many possible speakers who had to be weeded out.

Jackson disputed he was invited, saying: "That's not true."

Others due to speak include Sen. Al Gore, D-Tenn., a possible candidate who ran four years ago, well behind Jackson.

There are no official candidates yet for the party's nomination to be decided at the party convention after five months of state primaries and caucuses.

Former Massachusetts Sen. Paul Tsongas is due to announce on April 30 but is given little chance to win, having been out of office for over six years after quitting the Senate because of cancer. He says he has beaten the disease.

Tsongas will be a speaker at the event, as well as Arkansas Gov. Bill Clinton, a possible candidate.