Ammon News - AP - Palestinian President Mahmoud Abbas on Sunday called the Holocaust "the ugliest crime humanity has known in modern history," a rare acknowledgment by an Arab leader of Jewish suffering during the Nazi genocide.

Abbas also said he felt compassion for the victims and their families. Some 6 million Jews perished in the Nazi genocide during World War II.

His comments were published by the Palestinian official news agency WAFA just hours before the start of Israel's annual Holocaust memorial.

Abbas' statement also came as the latest U.S. 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 Hamas. At the time, Israeli leaders alleged Abbas preferred peace with the militants, who have called for Israel's destruction, to peace with Israel.

Abbas, meanwhile, has said he is ready to extend negotiations beyond Tuesday's deadline, provided Israel halts settlement construction and keeps a promise to release a group of veteran Palestinian prisoners. He said Saturday that any interim unity government with Hamas would be based on his political platform, not that of Hamas.

"What happened to the Jews is the ugliest crime humanity has known in modern history," he said, according to WAFA.

"On the memorial of the painful Holocaust, we call on the Israeli government to use this opportunity to reach a just and comprehensive peace, based on a two-state solution, Palestine and Israel living side by side in security and peace," he said.

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

Hamas has traditionally refrained from acknowledging the Holocaust and in 2009 protested against the subject being taught in United Nations-run schools in Gaza.