The Bureau of Alcohol, Tobacco and Firearms was preparing to ban importation of another 25 models of semiautomatic weapons but was ordered to hold off on the move by Treasury Department officials after the National Rifle Assn. raised objections, Administration sources said. James Jay Baker, a senior NRA officer, said that on Wednesday night the group learned that other weapons might be added to the list of five types of assault weapons that had been temporarily banned the day before at the request of drug czar William J. Bennett. It contacted Treasury officials, who said there would not be any new restrictions. Government officials said the bureau had informed importers that it was considering expanding the ban and had planned to announce the action Thursday. This new order would have covered many smaller, less-popular models.