The U.S. Ambassador to Spain warned the previous Spanish Prime Minister late last year that he risked putting his country on an American trade blacklist by failing to pass a law similar to the Stop Online Piracy Act. The warning came in a leaked letter reported by Spanish-language newspaper El Pais.

In the letter, dated Dec. 12, Ambassador Alan Solomont expresses "deep concern" over outgoing Prime Minister Jose Luis Rodriguez Zapatero's reluctance to pass the Sinde law, which would have prevented Spaniards from downloading content protected by copyright.

Solomont later warns that Spain, already on the United States' watch list for countries that do not provide "adequate and effective" protection of intellectual property, could be further degraded in status. Such a downgrade could result in trade restrictions between the two countries and potentially devastate the already fragile Spanish economy.

"The government of Spain made commitments to the rights owners and to the US government," Solomont says in the document. "Spain can not afford to see their credibility questioned on this issue."

Prime Minister Zapatero refused to sign the law before stepping down on Dec. 21. The new Spanish Prime Minister, Mariano Rajoy, adopted the Internet piracy bill on Dec. 30. On the same day, another letter leaked to Prime Minister Rajoy, reportedly sent by the head of the American Chamber of Commerce in Spain, urging him to take immediate action on the intellectual property issue.

This isn't the first sign of American influence in Spanish Internet legislation. In December of 2010, El Pais published a series of diplomatic cables leaked via WikiLeaks which revealed that the U.S. has been heavily involved in crafting Spanish intellectual property law. According to those cables, the White House had a heavy hand in decisions made by multiple parties in Spain's government.