A new coalition of preservationists says national parks across the country face threats from commercial development similar to a plan by a Virginia company to build a shopping mall next to the Manassas National Battlefield.

"At 175 parks, the threat is so significant that the reason the park was established may be lost," Paul Pritchard, one of the founders of the National Heritage Coalition, said Thursday.Pritchard said other endangered parks include Richmond and Fredericksburg-Spotsylvania in Virginia; Gettysburg, Pa.; the Everglades National Park in Florida; and Olympic National Park in Washington.

At a press conference, Pritchard and other opponents of the Manassas shopping mall announced their intention to stop it and any other proj-ect that endangers a historic site.

President Carter's former press secretary, Jody Powell, is helping the group free of charge with public relations and organized the gathering.

The coalition - sponsored by the National Trust for Historic Preservation and the National Parks and Conservation Association - is calling for Congress to enact legislation giving the federal government power to halt development temporarily so that negotiation, compromise or federal acquisition of disputed property can take place.

As part of its project to protect the Manassas battlefield, the coalition is working for passage of a bill recently introduced by Reps. Michael Andrews, D-Texas, and Robert Mrazek, D-N.Y., that directs the Interior Secretary to acquire the land now owned by developers.

Meanwhile, bulldozing is under way to prepare for townhouses and detached homes that will accompany the shopping mall. Bob Kelly, spokesman for the developer, Hazel-Peterson Co., said nothing can stop construction short of an act of Congress.

The acreage in question includes the site where Confederate Gen. Robert E. Lee directed troops for the second battle of Manassas and includes land used for hospital space and as a burial ground for some of the war dead.