Plans for the proposed National Harbor resort in Oxon Hill have been delayed because of a disagreement between federal agencies over the potential harm to the environment.

The National Capital Planning Commission, the central planning agency for the federal government in the Washington area, had been expected to make a decision by now on whether construction could begin on the 534-acre complex on the Potomac River shoreline. But as of this week, the commission had no vote scheduled on the development.

A spokesman for the developer and others close to the review process said the delay is the result of a dispute between the U.S. Environmental Protection Agency and the 12-member planning commission over the scope of its analysis of potential harm in a federally mandated environmental study.

Both draft and final versions of the study concluded that the project meets U.S. environmental requirements, including a legal mandate for "a thorough and balanced account of the potential effects of the proposed action under various development scenarios," according to the study.

But the EPA objects to the findings, said Ralph Spagnolo, an environmental scientist who helped conduct a review of the development for the agency's regional office in Philadelphia.

The final analysis "needed more information," Spagnolo said in a telephone interview. "We believe that there are still issues and that the impacts of the project would be high."

In a letter last month to the commission, Stanley Laskowski, director of environmental services for the EPA, criticized the planning agency for not studying more land-use alternatives than the retail and entertainment complex proposed by the developer and approved by the county.

The study focused on just three scenarios: a no-build option, construction of the National Harbor resort and construction of the PortAmerica project previously considered at the site.

"EPA has found that the [study] continues to inappropriately limit the range of alternatives considered for meeting the local objectives of economic development and regional tourism," Laskowski wrote in the letter. "Though we understand your basis for limiting consideration of lower density alternatives (because they did not conform to the county's authorized land-use plans), we must point out that . . . a potential conflict with local or federal law does not necessarily render an alternative unreasonable."

Denise Liebowitz, a spokeswoman for the commission, declined to comment.

Andre Gingles, a Calverton-based real estate lawyer who represents the National Harbor developer, Milton V. Peterson, questioned the EPA's concerns.

"What we have is someone in Philadelphia deciding that they are in a better position than someone in Prince George's to comment on land-use planning that has been going on for more than 20 years," Gingles said. "They don't like [the development]. They want to be able to tell the locals what to do."

But some opponents of the development praised the EPA for raising concerns that they share about the project and about the review process.

The commission "is not protecting the public interest at all," said Bonnie Bick, a spokeswoman for the Sierra Club, which is lobbying for a regional mall and Metro stop in downtown Oxon Hill instead of the riverfront complex.

Bill Shepard, a spokesman for the Maryland B.A.S.S. Federation, a fishing organization, also criticized the commission for not studying alternatives to commercial development at the site.

"We are delighted that the EPA thinks they have not looked at the whole scope of the project," Shepard said. "The NCPC is charged with protecting the interests of the Potomac River. It's significant if a body as powerful as EPA thinks the process wasn't followed correctly."