Calling Democratic politicians "timid" for their refusal to campaign directly against President Reagan, AFL-CIO President Lane Kirkland said here today that this fall's midterm elections may prove to be less than a referendum on the president and his policies.

On the unofficial Labor Day opening of the fall campaign, Kirkland said in an interview that there is "too much Tweedledum and Tweedledee" among Democrats in Congress and predicted the Democratic Party would gain no more than 20 House seats this fall, despite a current unemployment rate of 9.8 percent. He said that, on the basis of his travels and public opinion polls, he believed there had been "a substantial dropaway" of labor support for the president, whose 1980 victory was helped by a strong blue-collar vote.

"But how that translates into the midterm elections is open to debate," Kirkland said, "because Reagan isn't running."

"The economy is the key issue," he said, arguing that Reagan should be forced to answer personally for his policies. "But the Democrats in Congress have not drawn that issue too clearly."

"The Democrats," he added later, "are timid about making the argument against Reagan."

As a result, Kirkland said that "an essential change in American political life will not occur this fall. . . . It will only set the stage for . . . 1984."

Kirkland was in San Antonio along with the presidents of at least five international unions for a Labor Day celebration honoring Samuel Gompers, the founder of the American labor movement who died in San Antonio in 1924 while returning from a labor conference in Mexico.

At the celebration, which included the unveiling of a statue of Gompers that stands near San Antonio's charming Riverwalk and an hour-long parade past the historic Alamo, Kirkland continued his attack on Reagan and economic policies that Kirkland said have left 11 million people unemployed.

"This priceless asset -- what Gompers called 'the manhood and womanhood of our country' -- is being squandered by an administration that knows the price of everything in dollars and the value of nothing on the scale of humanity," he said.

He also quoted words of Gompers from 1914, which he said Reagan should listen to today.

"Gompers said, 'It is a false and unwise economy and a lack of statesmanship to retrench public expenditures and improvements when such course means suffering, misery and hunger. . . . This is a time to spend -- to spend wisely as well as humanely,' " Kirkland said.

He also noted Gompers' efforts to link American workers with those abroad. "If Gompers were with us today, his voice would be raised on behalf of the workers of Poland, and their leader, Lech Walesa, now in his 268th day of captivity, while the bankers continue to underwrite his jailers with cheap credit," he said.

But as he carried forth his opposition to Reagan in his public activities today, Kirkland expressed disappointment in his interview with the failure of many Democrats to do the same thing.

"When you've got a situation where the House Ways and Means Committee won't even tamper with a tax bill from the Senate because of the political implications of getting fingerprints on the bill, you don't have much of a fighting opposition," he said, referring to the $98.3 billion tax increase that originated in the Republican-controlled Senate and was passed by Congress with the support of the president.

He said too many Democrats are "fine tuning . . . calibrating," attempting "to look like they're putting up a fight, but they're not really."

Many Democrats say they continue to shrink from attacking Reagan directly, in part because they believe the president is personally popular and still perceived nationally as a decent man.

Kirkland disagreed. "I have a hard time thinking that someone who accepts these levels of unemployment is basically a nice person," he said.

Democratic timidity is only one factor that Kirkland said could make the midterm elections something other than a direct referendum on Reagan. The fact that 20 of the 33 Senate seats up this year are Democratic may render the Senate elections meaningless as a reading on the Reagan presidency.

On House races, Kirkland said reapportionment, which has added seats in the Southwest and West, where Reagan's policies are generally popular, while eliminating them in historically Democratic areas of the Northeast and Midwest, will muddy the outcome of the November elections.

He also said the "staggering" sums of money raised by conservative groups will be difficult to overcome by organized labor and the Democrats.

"I'm not pessimistic about our chances to win in spite of" the conservatives' edge in money, he said. "But it certainly is a problem."

The difference in money, he said, puts candidates favorable to labor at a tremendous disadvantage in gaining access to "the most powerful single influence in politics in the country today, television."

Organized labor, he said, would concentrate on 80 or 90 "marginal" House seats in an effort to build a coalition in Congress that will support labor's agenda.

Kirkland indicated he is eagerly awaiting the 1984 presidential elections, when labor, for the first time, may endorse a candidate for the Democratic nomination. A vote is scheduled for December, 1983.

Labor unions already are enjoying the benefits of this process, as Democratic aspirants line up to address their conventions. A smiling Kirkland noted, "It's a little better than in the McGovern days when everyone was running around saying labor's irrelevant."

Elsewhere around the country, three cities revived the traditional workers' Labor Day parade and unions blamed President Reagan for the worst unemployment in 40 years as Americans celebrated or mourned the state of organized labor on the 100th anniversary of the first Labor Day.

Burly ironworkers and high school bands marched in Indianapolis in the city's first Labor Day parade in 40 years. "In the past we may have concentrated too much on baseball games, picnics and fishing trips," said Loran Robbins, head of the largest Teamsters local in the state, which had an 11.1 percent jobless rate in July.

Marchers paraded down Michigan Avenue in Chicago's first Labor Day parade by organized labor in 30 years, and the first Labor Day parade since the 1940s rolled through Denver.

In New York, more than 150,000 union members marched in the 100th annual Labor Day parade down Fifth Avenue accompanied by 150 bands and 125 floats.

There were the usual rollicking celebrations on the three-day weekend that traditionally means the end of summer: raft regattas on the Missouri and Arkansas rivers and mud stomping in Maine.

And there were somber reminders of unemployment: parishioners at the A.M.E. Church in Baltimore were asked to offer jobs instead of money when the offering plates were passed around. Marchers in Racine, Wis., wore black armbands Sunday inscribed with 250,000, which march organizers said is the number of the state's jobless.

In the West Virginia coalfields, United Mine Workers President Sam Church called on Reagan to "listen to American labor."

"We can see the fundamental injustices of your policies," Church said.