(CNN) -- President Barack Obama's trip to Saudi Arabia this week comes amid accusations the State Department has hidden the results of a study that concludes textbooks in the Kingdom remain rife with Islamic extremism.
Since the September 11, 2001, attacks, successive U.S. administrations have attempted to curb Saudi indoctrination of students through hateful extremist material in its textbooks.
In addition to teaching the material to its own students, Saudi Arabia runs academies in about 20 countries, which use some of the same texts.
The Kingdom has repeatedly claimed that it has revised its textbooks.
In 2005, the Saudi government took out a full-page ad in the New Republic to boast of its success at "having modernized our school curricula to better prepare our children for the challenges of tomorrow."
But the Foundation for Defense of Democracies said on Tuesday the secret study finds Saudi textbooks still "create a climate that fosters exclusivity, intolerance, and calls to violence that put religious and ethnic minorities at risk."
Citing sources familiar with it, the Washington-based think tank said the Obama administration decided not to publish the study when it was completed in late 2012 because offensive material dehumanizing Jews and Christians included in the textbooks would portray the Saudis in a negative light.
"The State Department is in possession of a uniquely exhaustive set of recent findings about incitement in Saudi Arabia's education system, findings that it has declined to release for public consumption," the report said.
The study is the product of a reported $500,000 State Department contract with the International Center for Religion and Diplomacy.
On its website, ICRD says the project was commissioned to "assist in the ongoing effort by Saudi Arabia to remove discriminatory content from its public school curriculums and to evaluate its global impact in other Muslim-majority countries."
Current and former U.S. officials said the study paints a mixed picture of Saudi textbooks.
While it notes some progress by Saudis in making reforms and removing some of the most hateful language, the study still found areas for improvement.
"We know there's more work to be done," State Department spokeswoman Marie Harf said.
Ali Ahmed, a Saudi scholar who runs the Washington-based Institute for Gulf Affairs, has been studying Saudi textbooks since before the 9/11 attacks.
Ahmed said that in meetings with State Department officials over the years, he has found a consistent reluctance to put pressure on the Saudi royal family about the problem.
"I wrote papers and offered advice. I provided them with the textbooks showing evidence that the Saudis have not done anything," he said, adding that several officials warned him his campaign could damage U.S.-Saudi relations.
"The U.S. confronts China and Russia about human rights, but I don't know why they can't tell the Saudis to clean up their act on this issue," he said. "The U.S. is not a small country like Panama with no tools to force change. So either they are not serious or their policy is a failure here. If the U.S. wanted to bring some pressure, they can. They have not tried."
Harf said the United States has consistently and publicly encouraged Saudi Arabia to institute educational and textbook reforms, but disputed the notion that the State Department had ever planned to publish the study.
"It was intended to drive and inform the work of the State Department as we work with the Saudi government to push them to reform their textbooks," Harf said. "We obviously continue to push our partners to reform, and we believe with the Saudis that it's most effective to do this directly, with them, between our governments, and not publicly, and we do want to keep working with them to see if they can reform their curriculum more."
David Andrew Weinberg, a senior fellow at the Foundation for Defense of Democracies who wrote the study, said Saudi teachings of intolerance should be on the agenda when Obama visits the Kingdom this week.
"The hate speech so rampant in Saudi textbooks should be publicly addressed by the President while in Riyadh," Weinberg said. "Doing so would put hardliners on notice that even at this low point in U.S.-Saudi relations, the President will not shy away from affirming pluralistic American values and seeking reforms in the name of our national security."