The Palestinians took the last formal step Friday to join to join the International Criminal Court, seeking to pursue war-crimes charges against Israel related to the recent war in Gaza and to Jewish settlements in Palestinian territories.

The high-stakes move has drawn threats of retaliation from Israel and is vehemently opposed by the U.S. as an obstacle to reaching an Israeli-Palestinian peace deal.

After submitting the documents to join the ICC, Palestinian Ambassador Riyad Mansour said the Palestinians are seeking to raise alleged crimes previously committed by Israel, including those that occurred during last summer’s war in Gaza. He said the Palestinians will also be seeking justice for Israeli settlements on Palestinian territory, which he said constitute “a war crime” under the Rome statute that established the court.

“This is a very significant step,” Mansour told reporters. “It is an option that we are seeking in order to seek justice for all the victims that have been killed by Israel, the occupying power.”

The Palestinians moved quickly to join the court after suffering a defeat in the U.N. Security Council, which rejected a resolution Tuesday that would have set a three-year deadline for the establishment of a Palestinian state on lands occupied by Israel.

Joining the ICC is part of a broader strategy to pressure Israel into withdrawing from the territories and agreeing to Palestinian statehood.

Palestinian President Mahmoud Abbas has been under heavy domestic pressure to take stronger action against Israel after a 50-day war with between the Jewish state and rebels in Gaza over the summer, tensions over holy sites in Jerusalem and the failure of the last round of U.S.-led peace talks. He signed the documents to join the ICC a day after the Security Council rejected the resolution.

Israeli Prime Minister Benjamin Netanyahu immediately vowed to take unspecified “retaliatory steps.” The U.S. State Department said the Palestinian decision would only set back the aspirations of the Palestinian people for an independent state.

Mansour delivered the paperwork to Assistant Secretary-General for Legal Affairs Stephen Mathias, who said the U.N. will examine them to ensure that they are in proper form.

Mansour said it will take about 60 days under ICC rules for “the state of Palestine” to become the 123rd member of the court.

Mansour said the Palestinians delivered a letter Thursday night to the registrar of the ICC in The Hague requesting that the court consider alleged crimes committed during the Gaza war “and reserving our right for other retroactive crimes committed by Israel.” He said he would be meeting with an official from the registrar’s office in New York later Friday to discuss the issue.

Former ICC prosecutor Luis Moreno Ocampo said in an AP interview in August that the Palestinians have the right to decide that the court has jurisdiction dating back to November 2012, when the U.N. General Assembly voted overwhelmingly to upgrade the Palestinians’ status from a U.N. observer to a non-voting observer state. Ocampo said there should be “no discussion” on that.

The Palestinians could seek to have Israeli military or political figures prosecuted for alleged crimes involving settlement construction on occupied lands or actions by the military that cause heavy civilian casualties.

“Palestine’s move to join the ICC means that individuals implicated in war crimes committed in or from Palestinian territory could be held to account,” said Balkees Jarrah, international justice counsel at Human Rights Watch. “Giving the court a mandate may deter the abuses that fuel animosity and make returning to peace talks more difficult – whether settlement expansion, Israeli attacks on civilians in Gaza, or unlawful Hamas rocket strikes.”

But joining the court also exposes the Palestinians themselves to charges of war crimes over rocket attacks by Hamas on Israeli population centers and other violence against Jewish targets.

Mansour said the Palestinians aren’t afraid of justice.

“We uphold the law so high, and we are not afraid of the judgment of the law, especially international law,” he said.

The General Assembly’s recognition of Palestine as an observer state made it possible for the Palestinians to join the International Criminal Court.

Mansour also delivered to the documents for Palestine to join 15 other U.N. conventions, treaties and agreements.

These include the Nuclear Nonproliferation Treaty, the Law of the Sea convention, and the convention lifting the statute of limitations for war crimes and crimes against humanity. The Palestinians also joined conventions against transnational organized crime, and on the political rights of women, biological diversity, movement of hazardous waste and the safety of U.N. personnel. SAPA