Although authorities designed a plan to comply with the new law and the United States will not fully enforce it during the first two years, the government is not confident about powers granted to inspectors.

"The fear is not unfounded. We have seen this happen before, in Chile with grapes and in Mexico with strawberries," Javier Trujillo, the director of the National Food Quality Service, told EFE.

In 1989, the U.S. Food and Drug Administration placed an embargo on Chilean grapes after the discovery of two grapes tainted with cyanide at the port of Philadelphia.

The embargo led to US300 million in losses for Chilean producers and exporters although it was later proven that the grapes were contaminated in the United States.

In the case of Mexico, some children died in Minnesota six years ago after eating a dessert made with strawberries that supposedly came from this country, which caused exports to slip for two years.

On Nov. 21, the U.S. Food and Drug Administration issued an alert restricting imports from Mexico and said green onions from that country may have caused an outbreak of hepatitis A.

The United States is Mexico's main trading partner and is the destination of 90 percent of the country's exports, of which most are industrial goods but a significant quantity are agricultural products.

Mexico exports agricultural products valued at US7.5 billion to the United States each year, and fresh fruits and vegetables account for US2.5 billion of that total.

To avoid shipments being turned back, the secretaries of Health, Agriculture, Interior and State have met to determine what producers and exporters are complying with the new U.S. law.

Trujillo insisted "there is no evidence" that Mexico could be used as a location from which to launch bioterrorist attacks against the United States.

The new bioterrorism law provides that the FDA shall establish records containing the product's description, data on the exporter and producer and the date of the planned entry of the shipment into the United States.