(JTA) – In a newly revealed letter from 1986, Prince Charles suggested the “influx of foreign, European Jews” was a cause of turmoil in the Middle East and called for a U.S. president to “take on the Jewish lobby.”

After a visit to the Gulf with Princess Diana, Charles wrote to a friend that he had gained greater insight into the Arab world’s hostility toward Israel, the Daily Mail reported Saturday, Nov. 11. He suggested the arrival of Jews from Europe was a driver of terrorism.

“Also begin to understand their point of view about Israel. Never realized they see it as a US colony,” he wrote on Nov. 24, 1986. “I now appreciate that Arabs and Jews were all a Semitic people originally + it is the influx of foreign, European Jews (especially from Poland, they say) which has helped to cause great problems.”

In the next sentence, he said, “I know there are so many complex issues, but how can there ever be an end to terrorism unless the causes are eliminated?”

Many Jews consider Israel part of their ancient homeland and reject suggestions that they are outsiders in it.

Charles, who was 38 years old at the time, ended the letter to explorer Laurens van der Post by saying that he hoped that a U.S. president would stand up to the “Jewish lobby.”

“Surely some US president has to have the courage to stand up and take on the Jewish lobby in US? I must be naive, I suppose,” he said.

Some see the term “Jewish lobby” as invoking antisemitic canards that paint Jews as nefarious outsiders who seek to manipulate their countries for their own ends.

Campaign Against Anti-Semitism, a British watchdog for hatred of Jews, called Charles’ letter “unmistakably antisemitic.”

“This letter is disturbing. It appears that our future king believed in 1986 that the ‘influx’ of Holocaust survivors to Israel were not ‘Semitic,’ ‘cause great problems’ including terrorism, and should be ‘eliminated,’ presumably through their removal,” said the group’s chairman, Gideon Falter, in a statement Sunday. “The letter also appears to endorse the view that Israel is not simply the result of Jewish self-determination in the historic Jewish homeland, but the result of bullying by an all-powerful ‘Jewish lobby’ which holds US presidents in its clutches. We view these comments as unmistakably antisemitic.”

However, Falter said that since the letter was written, Charles “appears to have warmed to the Jewish community,” noting his friendship with Orthodox Jewish Rabbi Lord Jonathan Sacks, and his attendance at the inauguration of Ephraim Mirvis, Sacks’ successor as chief rabbi of the United Hebrew Congregations.

“In order to reassure the worldwide Jewish community, including Jews living in Israel, that the heir to the throne has changed his views, these historic remarks must urgently be repudiated by Prince Charles,” he said.

A spokeswoman for Charles said he was not expressing his views in the letter but only recounting those he encountered during this trip.

“He was sharing the arguments in private correspondence with a long-standing friend in an attempt to improve his understanding of what he has always recognized is a deeply complex issue to which he was coming early on in his own analysis in 1986,” the spokeswoman said.

She also said Charles “has continued his study of the complex and difficult themes he referenced here” and defended his “proven track record of support for both Jewish and Arab communities around the world,” in addition to promoting interfaith dialogue.

Despite numerous invitations over the years, no British royal has ever come to Israel on an official “royal tour.” Prince Charles attended the funerals of Israeli Prime Ministers Shimon Peres and Yitzhak Rabin, but did not hold diplomatic meetings on those trips.