The panel's report also criticized the current and former administrations in Washington for doing far too little to make basic religious rights universal.
That is the goal of the congressional act that founded the U.S. Commission on International Religious Freedom in 1998. The commission investigates conditions in what it calls "hot spots," where religious freedom is endangered. Its job is to recommend U.S. government policies to improve conditions.
It is a "small but critically important point of intersection of foreign policy, national security and international religious freedom standards," the report said. "Regrettably that small point seems to shrink year-after-year for the White House and he State Department."
This year's list of 13 "countries of particular concern" included all eight named last year — Myanmar, also known as Burma; China; Eritrea; Iran; North Korea; Saudi Arabia; Sudan; and Uzbekistan — plus Iraq, Nigeria, Pakistan, Turkmenistan and Vietnam.
U.S. actions currently in force against the original eight include embargoes, often on top of existing sanctions, and denial of military or financial aid. Sanctions have been waived indefinitely for Saudi Arabia, and Uzbekistan has a waiver of 180 days which remains in force.
President Barack Obama's administration has not officially accepted the 2009 findings or named the specified countries as violators of religious rights. Neither did the administration of President George W. Bush between November 2006 and January 2009.
In addition to the 13 designated the worst violators, the report identified 12 countries on a watch list: Afghanistan, Belarus, Cuba, Egypt, India, Indonesia, Laos, Russia, Somalia, Tajikistan, Turkey and Venezuela.
Thursday's report described violations of religious freedom in Saudi Arabia as "systematic, egregious and ongoing" despite limited reforms implemented by King Abdullah.
"In China, the government continues to engage in systematic and egregious violations of the freedom of religion or belief," the report said. It alleged "a marked deterioration in the past year, particularly in Tibetan Buddhist and Uighur Muslim areas."
It had similar observations for the other countries listed. In Iran, it noted "prolonged detention, torture and executions based primarily or entirely upon the religion of the accused." It said the Tehran government's record deteriorated after contentious elections in June.
The commission's chairman, Leonard Leo, said in a statement that visits to the "hot spots" had found situations "where freedom of religion is obstructed and related human rights are trampled."
He said the report offers important foreign policy solutions that should be implemented. "The report's conclusion is clear," Leo said: "the administration must do more."