President Carter yesterday signed an executive order sharply limiting the export of products that are banned or restricted from use in the United States.

Only a few products, perhaps a dozen, are expected to be banned out right from export when the process is fully in effect about six months from now. However, the order will make sure that hundreds of other banned or restricted foods, drugs, chemicals and devices will go only to governments that know exactly what they are getting and want it anyway.

"It emphasizes to other countries . . . that they can trust goods bearing the label, 'Made In U.S.A.,'" Carter said.

The incoming Republican administration is known to have asked for further delay in the policy, which has been 2 1/2 years and five drafts in the making by a 22-agency working group.

Esther Peterson, Carter's consumer affairs assistant, told a briefing session that President-elect Ronald Reagan clearly has the power to nullify the executive immediately upon taking office but added that she hoped he would see it as "a mechanism that is there to use if he wants to use it."

Peterson will "keep an eye on this" from the same kind of outsider consumer activist position she had before joining the government. "If it works, all right. If not, then maybe we'll need new legislation. It's not a dead issue," Peterson said.

Peterson and Robert Harris, a member of the Council on Environmental Quality, co-chaired the task force that began work on the policy in the wake of massive exports of children's sleepwear containing Tris, a cancer-causing fire retardant. The clothing was banned here in 1977, but exports continued abroad for more than a year, eventually totaling 2.4 million articles.

Other hazardous items -- including about 50 pesticides, aerosol sprays, many drugs and some X-ray equipment -- are made here solely for export, having either been banned for domestic sale or never having applied for domestic sales permits.

The order has four main parts:

Importing governments will be notified through the Department of State of all U.S. regulatory actions on a substance they seek to import, with all proven hazards spelled out.

The Regulatory Council will publish an annual summary of all U.S. regulatory actions that ban or restrict a product. This "could serve as a hazard alert for foreign governments that may be importing that substance from other countries," Peterson's statement said.

Efforts will be intensified toward international hazard labeling, notification and alert systems.

Products deemed "extremely hazardous" would be placed on the State Department's commodity control list, and the Commerce Department would only grant export licenses if the importing country, when fully informed, had no objection to the product.

Within 90 days, all regulatory agencies must compile lists of items they have banned or restricted from sale. About 400 are thought to exist. A special task force then will recommend to the State Department which items might meet the "extremely hazardous" criteria: They must represent a "substantial threat to human health or safety or to the environment"; they must cause "clear and significant harm" to foreign policy interest; and they would get export licenses only in "exceptional cases."

Only items meeting all three criteria will be placed on the commodity control list. "It is the intent of this policy to rely primarily on notification procedures, with controls being used in only a very few instances," the White House fact sheet said.

Jacob Scherer of the Natural Resources Defense Council said he was very pleased with the policy and hoped only that export bans would follow quickly after domestic ones.

However, Lewis A. Engman, president of the Pharmaceutical Manufacturers Association, called the order an "11th-hour act of arrogance" that would cost American jobs. It will "ensure that sales go to foreign firms," he said.