The controversial agreement banning sales of three-wheeled all-terrain vehicles contains a provision that could allow ATV makers to resume sales this year, industry spokesmen and government officials said yesterday.

Less than 24 hours after the Justice Department and Consumer Product Safety Commission hailed a consent decree as marking an end to sales of what they described as the most dangerous ATV model, industry spokesmen were speaking of returning the three-wheel series to the American market, perhaps within months.

"I think they're sadly mistaken," said safety panel chairman Terrence M. Scanlon, who said he saw no way the commission would allow the models to return to dealer showrooms. "If the consent decree results in the resale of three-wheelers, it would be a disaster," said Commissioner Anne Graham, the one member of the three-member safety panel to vote against accepting the decree.

A spokesman for American Honda Motor Corp., which has been the leading ATV seller, however, cited a provision in the decree that allows renewed sales of the three-wheeled ATVs after the safety commission sets certain standards, and said their return is "definitely a real possibility."

Kurt Antonius, the Honda spokesman, said his firm will store the 18,000 three-wheel models currently in dealer inventories in hopes of returning them to the market with government approval in several months.

A spokesman for Yamaha Motor Corp., another major importer of the off-the-road vehicles, described the court decree as a "moratorium" and said his firm also hopes to have the three-wheel models back on sale after minor modifications.

"All of the companies have taken the position that the machines are safe and that any problems are due to consumer misuse," said Mike Schmitt, a Yamaha spokesman.

James V. Lacey, general counsel for the safety commission, acknowledged yesterday that the agreement allows resumed sales of three-wheeled ATVs, but he said it is highly unlikely the commission would agree to standards that the three-wheel models could meet.

"From our review of the evidence I don't see how any modification of the machines would allow them to be reintroduced into the market," Lacey said. Scanlon said it would take "some phenomenal new technology" for the models to be made safe.

Lacey noted that the commission's ATV task force had declared that one problem with the vehicles was their "inherent instability" and said he doubted the vehicles affected by the ban could be easily modified.

The 23-page consent decree, signed by the five major ATV makers, contains a provision not mentioned during an hour-long news conference Wednesday at the Justice Department. It directs the industry "to attempt in good faith to reach agreement on voluntary {ATV safety} standards satisfactory to the commission within four months" of court approval of a final decree. That order should be entered in about 45 days, officials have said.

"To the extent that three-wheeled ATVs meet mandatory standards promulgated by the commission or voluntary standards satisfactory to the commission . . . the marketing and sales of such vehicles shall be permitted . . . , " the agreement says.

Lacey said that provision was incorporated into the decree in an effort to force the ATV industry to move toward production of a safer machine, an effort that had achieved little progress until the commission threatened to sue over the issue.

Commissioner Graham said the statements by Honda that it hopes to resume sales of the three-wheel models support her earlier claims that the industry was unconcerned about the safety of the machines. "It is a sorry beginning for good-faith negotiations" over various safety issues that are to follow the decree, she said.

Graham also expressed concern yesterday about the safety agency's ability to enforce the court decree. The commission does not have sufficent staff to police ATV dealerships to make certain they have ceased sales of the three-wheel models.

"I am worried about dealers marking down the models and trying to move them out very quickly," she said.

Antonius said in an interview that he doubts his firm, which handles imports from Honda Motor Co. of Japan, could force dealers not to sell the three-wheeled models. The court decree directed Honda and other makers to notify their dealers within five business days of Wednesday to halt sales of the three-wheelers and to repurchase any the dealers have on hand. The decree does not say what the distributors must do with the banned models.

Wednesday's agreement calls for an end to sales of the three-wheel vehicles, which the commission branded as an "imminent hazard" in 1986, and for the industry to take various steps to educate ATV purchasers about the hazards of driving the vehicles.

Congressional opponents and consumer groups attacked the agreement, saying it abandons a commission request to seek refunds for purchasers of the three-wheeled models. Critics of the settlement also said it was meaningless because ATV makers were planning to discontinue making the three-wheel models in 1988.