The United States warned key ally Germany on Monday that it should do more to stop a tide of sex workers arriving for this month's soccer World Cup, and accused 12 nations of failing to do enough to stop the modern-day slave trade in prostitutes, child sex workers and forced laborers.

"The U.S. government opposes prostitution," which is legal in Germany, a State Department report on global human trafficking said. "These activities are inherently harmful and dehumanizing."

A U.S. congressman and other anti-trafficking advocates estimate that thousands of foreign women, many from Eastern Europe, will be forced into sex work during the four-week tournament that begins June 9.

At a briefing, Secretary of State Condoleezza Rice denounced "the sordid trade in human beings" and said the fight against trafficking is "a great moral calling of our time."

"Together we will stop at nothing to end the debasement of our fellow men," she said.

The United States called Germany a "source, transit and destination country" for sex workers and other victims of exploitation. The 2006 Trafficking in Persons Report still gave Germany its highest overall rating for compliance with effort to stop trafficking, and noted German efforts to combat exploitation during the World Cup.

"Nonetheless, due to the sheer size of the event, the potential for increased human trafficking during the games remains a concern," the report said.

As many as 800,000 people are bought and sold across national borders annually or lured to other countries with false promises of work or other benefits, the State Department said in its annual survey of international human trafficking. Most are women and children.

The report lists Iran and Syria among the dozen nations that the United States said do not adequately address trafficking problems. The State Department said those countries could be subject to sanctions.

Apart from Arab ally Saudi Arabia and the Central American nation of Belize, the rest of the list of violators reads like a catalog of nations at perpetual odds with the Bush administration: Myanmar, Cuba, Iran, Laos, North Korea, Sudan, Syria, Uzbekistan, Venezuela, Zimbabwe.

Countries that fail to crack down can be subject to a variety of sanctions, including the withholding of some kinds of U.S. foreign aid. The United States will not cut off trade and humanitarian aid, the report said.

Countries that receive no such assistance can be declared ineligible to take part in cultural and educational exchange programs.

Two countries have been sanctioned since the reports began — Equatorial Guinea and Venezuela.

The German government, while defending its policy of legalized prostitution, emphatically denies that it condones human trafficking and says it has intensified efforts to combat it.

Rep. Christopher Smith, R-N.J., chairman of the House subcommittee on global human rights, urged Germany last month to recriminalize prostitution and suggested that it should be reclassified as an "egregious violator" of human trafficking.

Germany's sex-industry entrepreneurs have made no secret of their expectation of a boom as hundreds of thousands of visitors arrive for the World Cup. At the four-story, 40-bedroom Artemis brothel which opened in Berlin last fall, manager Egbert Krumeich predicted business — normally 130 clients a day — could double or triple during the 32-nation tournament.

Prostitution is legal in Germany, with about 400,000 registered sex workers who pay taxes and receive social benefits. However, the government says forced prostitution is not tolerated and it denies Smith's claim that it is helping build brothels.

The German Embassy in Washington said German federal officials were working closely with regional authorities and nongovernment organizations to combat trafficking and forced prostitution, especially in the 12 World Cup host cities.