For the first time, the United Nations will officially commemorate the flight of hundreds of thousands of Palestinians from what is now Israel on the 75th anniversary of their exodus — an action stemming from the U.N.'s partition of British-ruled Palestine into separate Jewish and Arab states.

Palestinian President Mahmoud Abbas is headlining Monday's U.N. commemoration of what Palestinians call the "Nakba" or "catastrophe."

Riyad Mansour, the Palestinian U.N. ambassador, called the U.N. observance "historic" and significant because the General Assembly played a key role in the partition of Palestine.

"It's acknowledging the responsibility of the U.N. of not being able to resolve this catastrophe for the Palestinian people for 75 years," Mansour told a group of U.N. reporters recently.

He said "the catastrophe to the Palestinian people is still ongoing:" The Palestinians still don't have an independent state, and they don't have the right to return to their homes as called for in a General Assembly resolution adopted in December 1948.

Israel's U.N. ambassador, Gilad Erdan, condemned the commemoration, calling it an "abominable event" and a "blatant attempt to distort history." He said those who attend will be condoning antisemitism and giving a green light to Palestinians "to continue exploiting international organs to promote their libelous narrative."

The General Assembly, which had 57 member nations in 1947, approved the resolution dividing Palestine by a vote of 33-13 with 10 abstentions. The Jewish side accepted the U.N. partition plan and after the British mandate expired in 1948, Israel declared its independence. The Arabs rejected the plan and neighboring Arab countries launched a war against the Jewish state.

The Nakba commemorates the estimated 700,000 Palestinians who fled or were forced from their homes in 1948.

The fate of these refugees and their descendants — estimated at over 5 million across the Middle East — remains a major disputed issue in the Arab-Israeli conflict. Israel rejects demands for a mass return of refugees to long-lost homes, saying it would threaten the country's Jewish character.

As the 75th anniversary approached, the now 193-member General Assembly approved a resolution last Nov. 30 by a vote of 90-30 with 47 abstentions requesting the U.N. Committee on the Exercise of the Inalienable Rights of the Palestinian People organize a high-level event on May 15 to commemorate the Nakba.

The United States was among the countries that joined Israel in voting against the resolution, and the U.S. Mission said no American diplomat will attend Monday's commemoration.

Explaining why a U.N. commemoration took so long, Mansour told The Associated Press on Friday that the Palestinians have moved cautiously at the United Nations since the General Assembly raised their status in 2012 from a non-member observer to a non-member observer state.

U.N. recognition as a state enabled the Palestinians to join treaties, take cases against Israel's occupation to the International Criminal Court and the International Court of Justice, which is the U.N.'s highest tribunal, and in 2019 to chair the Group of 77, the U.N. coalition of 134 mainly developing nations and China, he said.

At the 70th anniversary of the 1948 exodus five years ago, Mansour said, "the word Nakba was used in a General Assembly resolution for the first time," and Abbas then gave instructions to obtain a mandate from the U.N. to commemorate the 75th anniversary.

The Nakba commemoration comes as Israeli-Palestinian fighting has intensified and protests over Prime Minister Benjamin Netanyahu's right-wing government and its plan to overhaul Israel's judiciary show no sign of abating. Israel's polarization and the Netanyahu government's extremist positions have also sparked growing international concern.

Mansour said Friday that Palestinian refugees "are being forcibly removed from their homes and forcibly transferred by Israel at an unprecedented rate," reminiscent of 1948.

In a speech to the U.N. Security Council on April 25, Palestinian Foreign Minister Riyad Malki said "it is time to bring the Nakba to an end," stressing that the Palestinians have suffered from the most protracted refugee crisis in the world and "the longest occupation of an entire territory in modern history."

He was sharply critical of the U.N. and the wider international community for adopting resolutions that make demands and call for action— but doing nothing to implement them. He said if the international community made Israel's occupation costly, "I can assure you it will come to an end."

Malki renewed his call for countries that haven't yet recognized the state of Palestine "to do so as a means to salvage the moribund two-state solution." He also urged countries to support the Palestinian request for full membership in the United Nations, which would demonstrate international support for a two-state solution where Israelis and Palestinians lived side-by-side in peace.

To hurt Israel economically, Malki urged countries to ban products from Israeli settlements and trade with settlements, to "sanction those who collect funds for settlements and those who advocate for them and those who advance them," and to list settler organizations that carry out killings and burnings as "terrorist organizations."

And he urged the international community to take Israel to the International Court of Justice. The General Assembly asked the court in December to give its opinion on the legal consequences of Israel's occupation of Palestinian territories, a move denounced by Israel.