With organized labor bracing for another possible loss in Congress, House Democratic leaders conceded yesterday that one or more key elecments of a bill to raise the minimum wage may be in trouble when the legislation comes up for a vote today.

Although the basic proposal to raise the hourly wage floor from $2.30 to $2.65 next year is expected to pass, major battles are shaping up over.

The bill's provision for automatically increasing the wage floor in the future by setting it at a certain percentage of average manufacturing wages, as opposed to the present system of setting a specific dollars-and-cents figure every few years.

A proposed amendment to provide a lower "subminimum" wage for teenagers, a long-standing Republican and business-backed idea that has attracted some support among younger Democratic liberals who see it as a possible tool to reduce youth unemployment.

A provision of the bill that would gradually raise the minimum wage that must be paid to waiters, waitresses and other workers who get tips and are now required to be paid only $1.15 an hour, or half the regular minimum wage.

The AFL-CIO has thrown its weight behind the entire bill in the first major test of its clout since the surprise defeat last March of the common sites picketing bill which would have made it easier for unions to shut down entire construction sites.

Since that time, the federation has joined forces with civil rights and women's groups and has comprised its position to get White House support in hopes of winning its way on the minimum wage bill and on labor law overhaul legislation that is next on its congressional agenda.

The tip credit modification, which is the only major part of the wage measure that is opposed by the White House, is considered the most vulnerable to attack and the one that labor could lose without suffering another serious blow to its prestige.

Rep Phillip Burton (D-Calif.), floor manager for the bill, said he thinks the bill will be approved without major change, although some members may split their votes to please both sides, making a precise forecast difficult. He said he believes labor has done an effective lobbying job on the measure.

However, House Speaker Thomas P. (Tip) O'Neill Jr. (D-Mass.) told reporters yesterday that a "tough battle" is anticipated on the youth differential, noting that some of the opposition "comes from our own side and we've go difficulty with it."

Rep. Robert J. Cornell (D-Wis.) is sponsoring an amendment to allow youths under age 19 to be hired at 85 per cent of the minimum wage for the first six months of their employment, and the margin of victory or defeat for the proposal could come from liberal Democrats.

As of yesterday, nose counts indicated that the leadership did not yet have the votes to defeat a youth subminimum wage, a source said.

The outlook on the automatic escalator, which the bill's proponents view as its most crucial provision, is murky. Majority Whip John Brademas (D-Ind.) said it looks "tough," but O'Neill said labor spokesman have told him that they have the votes for passage.

Under this provision, the wage floor would be set at 52 per cent of average manufacturing wages in 1979 and 53 per cent thereafter, which is expected to produce a floor of $2.89 in 1979, $3.15 in 1980 and $3.37 in 1981.

Labor lobbyists were claiming to be ahead on the escalator, "very close" on the youth differential and "50-50" on the tip provision. Business lobbyists said they were confident of winning on everything but the escalator and hopeful about that.

Both labor and business lobbyists have been crawling all over Capitol Hill in recent days, focusing primarily on wavering members. "It's fierce on both sides," said an aide of one of their targets.

Meanwhile, the Senate Human Resources Committee, as expected, approved a minimum wage bill that generally parallels the pending House measure. The vote was 14 to 1 on the bill, with roughly a 2-to-1 ratio on major amendments, indicating that the bill may be in better shape in the Senate than the House.