JERUSALEM — President Mahmoud Abbas of the Palestinian Authority issued a formal statement on Sunday calling the Holocaust “the most heinous crime to have occurred against humanity in the modern era” and expressing sympathy with victims’ families.

The statement, which grew out of a meeting a week ago between Mr. Abbas and an American rabbi who promotes understanding between Muslims and Jews, is the first such offering of condolences by the Palestinian leader.

Mr. Abbas has been vilified as a Holocaust denier because in his doctoral dissertation, published as a book in 1983, he challenged the number of Jewish victims and argued that Zionists had collaborated with Nazis to propel more people to what would become Israel. A senior Israeli minister, incensed at quotations from Hitler highlighted on Facebook pages affiliated with the Palestinian Authority, denounced Mr. Abbas earlier this year as “the most anti-Semitic leader in the world” at a conference in Tel Aviv.

Mr. Abbas had already backtracked from the book, saying in a 2011 interview that he did “not deny the Holocaust” and that he had “heard from the Israelis that there were six million” victims, adding, “I can accept that.”