By James Cox, USA TODAY

The Castro regime is using its checkbook as leverage to get U.S. firms, trade groups and politicians to sign formal pledges agreeing to work for changes to U.S. laws that restrict travel and trade with Cuba.

Cuba's use of so-called advocacy agreements has prompted anti-Castro lawmakers to accuse signers of illegal lobbying. It also has forced at least one company to rethink its interest in selling to Cuba.

Last month, Sysco, the country's largest food-service provider, notified Cuban authorities it was tearing up an agreement signed a week earlier by a Sysco executive attending a convention in Havana.

The original deal called for Cuba's state-owned purchasing arm, Alimport, to buy Sysco products. For its part, the company agreed to act as an advocate for changes in the United States' hard-line policies toward Cuba, including the 45-year-old economic embargo.

The embargo was loosened in 1992 to permit sales of U.S. medical products to Cuba and in 2000 to allow for cash-only sales of food and farm products. Through July, U.S. companies had sold $277 million in food and agricultural goods to Cuba, along with $500,000 worth of health care products.

The Bush administration has sought to tighten the economic noose on Cuba with tough new restrictions on travel and money transfers by Cuban exiles.

Sysco has sold $500,000 worth of canned tomatoes, ice cream and frozen produce to Cuba, spokeswoman Toni Spigelmyer says. The Houston-based company tore up its agreement with Alimport because the executive who signed it "wasn't authorized to make a political statement," she says.

Cuba has carefully spread its spending among scores of congressional districts in dozens of states to build political support for an end to the embargo.

Others that have signed advocacy agreements: the Indiana Farm Bureau; Tampa's Port Manatee; economic development officials from Des Moines; and elected officials from Idaho, Montana, California, South Carolina and Kansas.

The agreements are "a corruption of the commercial process" and a setback for efforts to expand trade with Cuba, says John Kavulich, president of the U.S.-Cuba Trade and Economic Council, based in New York.

Rep. Loretta Sanchez, D-Calif., and her sister, Rep. Linda Sanchez, D-Calif., signed to promote Cuba's purchase of California farm products, says Loretta Sanchez. She says the pledge is non-binding.

"We're trying to get our California products sold to Cuba. That's what I do as a congresswoman," Sanchez says. "I've already been vigorous and forceful in advocating a change in U.S. policy. ... The dissidents fighting the Castro regime want this embargo down."

Rep. Peter Deutsch, D-Fla., and other hardliners in Congress say the agreements might violate U.S. law, either as embargo-busting contracts or as illegal lobbying agreements. "Effectively, (those who sign) become agents of a foreign government," Deutsch says.

Last year, the State Department asked the Treasury, Commerce and Justice departments for opinions on the legality of the advocacy agreements. It has not received a formal reply.

Efforts to reach officials at the Cuban Interests Section in Washington were unsuccessful.