BEIJING (Reuters) - Beijing on Thursday ordered a suspension of history exams run by a U.S. non-profit for students seeking credit at American colleges, as the ruling Communist Party cracks down on educational material it deems unfriendly.

FILE PHOTO: Students study ahead of the entrance exam for postgraduate studies, at a library in Zhengzhou University in Zhengzhou, Henan province, China December 13, 2017. REUTERS/Stringer

The suspension of Advanced Placement (AP) tests will hit secondary school students looking to ease the academic workload at U.S. universities by earning credit for some college courses, enabling them to graduate faster.

Five testing centres across the cities of Beijing, Guangzhou, Nanjing and Shanghai confirmed to Reuters that they would suspend the tests by 2020, after a directive from China’s education ministry.

“This is a bit sudden, we don’t know the reason,” a Nanjing-based center, SAT Test Web, said in a posting on social media site WeChat.

“If you apply for any of these four subjects, it means you need to go to other exams outside the mainland.”

The tests affected are in U.S. History, World History, European History and Human Geography, said the International Exchange and Cooperation Centre in Educational Measurement (IECC), a Chinese body authorized to administer the exams.

China’s education ministry did not respond to a request from Reuters for comment.

Officials at AP testing centres in China who spoke to Reuters declined to comment on the reason for the ban, but said they would follow it to avoid punitive measures.

However, advanced courses and exams in science, mathematics and other subjects remain unaffected, the centres confirmed.

The College Board, a U.S. non-profit that works with the IEEC and receives fees for offering the exams globally, declined to comment directly on the suspensions or the numbers of students taking AP history exams in China.

A spokesman for the New York-based College Board said it had never moved to deny students access to AP exams, which, outside the United States, are “relatively rare and dependent on the willingness and ability of a school to administer the classes.”

It was not immediately clear what proportion the affected exams constitute of those taken in China.

The suspensions come as Beijing ramps up efforts to expunge educational history content that is not approved by the Chinese Communist Party.

Negative interpretations of topics as the Tiananmen crackdown, the Sino-Japanese War and the South China Sea are strictly censored in China, where cyber laws make it a criminal offence to share non-sanctioned history online.

Last September the education ministry launched an inspection of school textbooks to strip out unapproved content, and re-focus education on Communist ideology and history.

This month, it warned students and academics against the risks of studying in the United States, pointing to visa restrictions.

The move also comes amid rising U.S.-China acrimony as President Donald Trump’s administration takes a harder line on immigration, with Chinese students becoming a focal point of tension between the world’s two biggest economies.

China is the United States’ largest single source of foreign students, with the Institute of International Education putting their numbers at 363,000 in the 2017-18 academic year.