Palestinian President Mahmoud Abbas said on Sunday the Holocaust was "the most heinous crime" of modern history and expressed his sympathy for the victims, a rare acknowledgment by an Arab leader of Jewish suffering during the Nazi genocide.

Abbas' comments appeared, in part, aimed at reaching out to Israeli public opinion at a time of deep crisis in Israeli-Palestinian peace efforts. The remarks were published by the Palestinian official news agency WAFA just hours before the start of Israel's annual Holocaust commemoration.

The decades-old conflict has been accompanied by mutual mistrust among Israelis and Palestinians about each other's intentions.

Many Israelis fear that the Palestinians aren't truly ready to accept a Jewish presence in the Holy Land and that widespread ignorance or even denial of the Holocaust among Palestinians is an expression of that attitude.

Many Palestinians fear that if they acknowledge the Holocaust, they will diminish their own claims based on years of suffering, including their uprooting during Israel's 1948 creation and decades under Israeli occupation.

Abbas' office said he discussed the Holocaust in a meeting with a US rabbi, Marc Schneier, who visited Abbas' headquarters in Ramallah last week.

Abbas told Schneier that "what happened to the Jews in the Holocaust is the most heinous crime to have occurred against humanity in the modern era," WAFA said in a statement in English published on Sunday.

The wording in an earlier WAFA statement in Arabic was slightly different, with Abbas using the phrase "ugliest crime" instead of "the most heinous crime."

In the English statement, WAFA quoted Abbas as expressing his "sympathy with the families of the victims and many other innocent people who were killed."

Abbas said the Holocaust was an expression of the idea of ethnic discrimination and racism, and he made a connection to Palestinian suffering of today.

"The Palestinian people, who suffer from injustice, oppression and (are) denied freedom and peace, are the first to demand to lift the injustice and racism that befell other peoples subjected to such crimes," he said.

Abbas' statement came as the latest US attempt to broker an Israeli-Palestinian peace deal was on the verge of collapse.

Last week, Israel suspended negotiations in response to a reconciliation deal between Abbas and his political rival, the Islamic militant group Hamas. The group has traditionally refrained from acknowledging the Holocaust and in 2009 protested against the subject being taught in UN-run schools in Gaza.