Leaders of the AFL-CIO today reaffirmed organized labor's plan for a possible early presidential endorsement in 1988, ignoring previous warnings from Democratic National Committee Chairman Paul G. Kirk Jr. that such an action could hurt the eventual Democratic nominee.

AFL-CIO President Lane Kirkland, who was criticized in the 1984 campaign for spearheading the unprecedented pre-primary endorsement of Democrat Walter F. Mondale, has pushed strongly for a reaffirmation of his policy, which allows for an early endorsement if two-thirds of the unions representing 13 million AFL-CIO members agree on a candidate.

"We are not selecting a candidate, we are reaffirming a process," Kirkland said in an interview. "The important thing is that we intend to stay unified, if possible, in whatever we do, and not split ourselves in a variety of directions."

The AFL-CIO endorsement, which put the full muscle and money of labor's political machinery behind the Mondale campaign, was widely criticized as providing opponents with ammunition to accuse Mondale of being a captive of labor's "special interest."

Kirk, who is here attending the 30th anniversary convention of the AFL-CIO, has called on unions to "strengthen the party's nominee by refraining from an early endorsement."

In a March speech to the Communications Workers of America, Kirk said early endorsement by the labor federation could tip the balance of primary campaigns before the most viable Democratic candidate emerges.

"Let the candidates use the primary process to develop and to demonstrate their own broad political appeal and their own strong political base before giving one your full and united backing," Kirk said in his CWA speech.

Asked about Kirk's criticism of the early endorsement process, Kirkland said, "It is not his call. We are a self-governing body, and this is our business." Kirk could not be reached for comment today.

Union political operatives said today that Democratic Party rules virtually require an early AFL-CIO endorsement if the federation wants to mount a strong effort on behalf of a particular candidate. Those rules, in some primary states, require slates of committed delegates to be formed more than a year before the election.

"If you don't get an inside track early, you are locked out," said John Perkins, head of the AFL-CIO Committee on Political Education. He said that if the federation had not endorsed Mondale in October 1983, it would have been unable to place labor delegates on Mondale slates in 13 states.

"We are in politics to stay, and this resolution backs that up . . . . This is the kind of action a majority of our members support," said Thomas R. Donahue, AFL-CIO secretary-treasurer.

Several union leaders, including some who have supported Republicans, have opposed early endorsement. But today's resolution was passed without opposition among the 35 union executives.

The early endorsement strategy grew out of the bitter internecine political wars among unions such as 1980, when many AFL-CIO unions backed President Jimmy Carter's reelection bid, but a substantial number bolted quickly to back the challenge by Sen. Edward M. Kennedy (D-Mass.).

The resolution, which is expected to be adopted by the AFL-CIO convention later this week, asks the 96 affiliated unions to refrain from making an endorsement until the labor federation determines whether there is clear support for a particular candidate.

If a consensus candidate emerges, the AFL-CIO would make a pre-primary endorsement at its 1987 convention. If not, unions would make their own.

"This all may be a moot point," said Kenneth Blaylock, president of the American Federation of Government Employees and an executive council member. "We are reaffirming the process, but we may not have a candidate."

In a related development, the AFL-CIO executives also said they will seek a new mechanism to funnel more money into state AFL-CIOs, which in many states are considered woefully underfunded, even though it may involve a dues increase.