The dockworkers who have been leading labor's charge against the Ocean Shipping Reform Act of 1995 have now attracted a powerful ally - the 13 million-member AFL-CIO.

Ending public tariff filing, abolishing the Federal Maritime Commission and other reforms proposed in Congress "will shift cargo between ports" in a way that will put "smaller ports at a disadvantage," said Bill Cunningham, the AFL-CIO's chief lobbyist.The AFL-CIO opposes both the stand-alone bill advanced to the House floor from the Transportation Committee and the maritime deregulation rider attached to the sweeping budget plan currently under consideration, he said. A Senate version of the House bill was introduced late Monday by Sen. Larry Pressler, R-S.D.

The AFL-CIO is expected to make its deregulation opposition formal in a resolution adopted this week at its biannual convention in New York. The position statement says changes to existing shipping law would be harmful to U.S. workers, and calls on union affiliates to demand that hearings be held.

Assessments vary on the clout the AFL-CIO's opposition will carry in the Republican-led Congress.

Labor's concerns could put the bill "on hold, and maybe push a vote on it back to next year," said a senior House Republican staffer.

Such action could occur in the likely event the rider is stripped from the House budget reconciliation bill in conference with the Senate or if the giant spending bill is vetoed by the president.

AFL-CIO opposition "could have quite an effect, particularly on Democrats who have supported labor positions and any members representing port states," said William Hathaway, who chairs the FMC and is an outspoken critic of deregulation legislation. The labor stand could change a lot of minds and "be enough to defeat the bill," Mr. Hathaway said.

To Ed Emmett, president of the National Industrial Transportation League, a leading shippers group supporting deregulation, the impact of labor's action ''depends on how it is perceived" by lawmakers.

"It's clear they (AFL-CIO) are protecting a very narrow section of labor, as opposed to taking" a view of jobs in the economy as a whole, Mr. Emmett said.

Two seagoing union officials attending the federation's New York convention said they disagreed with the AFL-CIO resolution, although they downplayed their conflict with shoreside unions. Neither official would speak on the record.

"We're not in favor of" the resolution, said a top official of one seagoing union. "We don't want to screw up" ship-operating subsidy legislation, he said - a reference to the possibility that some southern senators may twin deregulation and government aid to U.S.-flag ship operators to defray higher U.S. labor costs.

Majority Whip Trent Lott, the Senate's second-ranking Republican and a key maritime industry supporter, is skeptical of the House shipping deregulation proposal. A Lott staff aide said Friday, however, that "bits and pieces" of the deregulation plan might be packaged with a reform of cargo preference funding and vessel operating subsidies early next year.

A staff member of the Senate Commerce, Science and Transportation Committee said Tuesday Sen. Lott will probably package the vessel operating subsidy bill already passed by the committee with separate legislation to reform Amtrak and to dismantle the Interstate Commerce Committee. That bundle of legislation will probably be sent to the Senate floor within two weeks.

Despite their concerns, seagoing union officials said they were unlikely to speak against the anti-deregulation resolution when it is taken up at the convention.

A transportation union official said he understood the seagoing union's position. "They're getting a lot of heat from their major U.S. employer," he said, meaning Sea-Land Service Inc.

Sea-Land, the largest U.S. shipping line, and the NIT League, are credited with crafting the industry agreement that is the basis for congressional shipping reform proposals. Sea-Land, along with other U.S.-flag lines, also has been a strong proponent of legislation that would continue ship-operating subsidies, possibly at a rate of $100 million a year over 10 years.

Though it is not spelled out in the AFL-CIO resolution, deregulation opponents generally argue that proposed reforms will lead to cutthroat competition resulting in fewer shipping lines calling at fewer ports. Proponents argue that efficiencies gained in a more competitive marketplace will enhance U.S. trade, possibly weeding out the least needed infrastructure.

Similar resolutions stating labor's opposition have been approved by the AFL-CIO's Transportation and Maritime Trades departments, and by individual unions like the International Longshoremen's Association, the International Longshoremen's and Warehousemen's Union and railway unions, among others.

Unions that represent shoreside maritime workers became concerned about the bill when they concluded it would repeat the "past mistakes of deregulation," said Ed Wytkind, executive director of the Transportation Trades Department.

When airlines were deregulated in the 1970s, Mr. Wytkind argued, ''predatory pricing" practices of some airlines soon "wiped out the founders of the airline industry." The unions, he said, believe ''deregulation has been an unmitigated disaster" for transportation workers and will be repeated when shipping goes through the same process.

"We're telling people, for god's sake, hold a hearing," Mr. Wytkind said.