Palestinian leader Mahmoud Abbas accused Israel on Friday of a "genocidal crime" in Gaza, saying the United Nations negotiations had failed and the time for Palestinian independence had come, drawing a sharp rebuke from Washington.

Abbas vowed to seek war crimes prosecutions against Israel over what he called the 50-day "war of genocide" in Gaza that killed 2,140 Palestinians, mostly civilians, and left the enclave in ruins.

The address angered the United States, which slammed it as "offensive," while Israeli Foreign Minister Avigdor Lieberman accused Abbas of waging "diplomatic terrorism" and making "false accusations."

Speaking at the UN General Assembly in New York, a feisty Abbas said, "There is an occupation that must end now. There are people that must be freed immediately.

"The hour of independence of the state of Palestine has arrived."

He did not set a deadline for fast-tracking Palestinian statehood, but aides have suggested they were eyeing 2017 as a possible date.

Describing Israeli attacks on Gaza as a "genocidal crime," Abbas pledged, "We will not forget and we will not forgive, and we will not allow war criminals to escape punishment."

The Palestinians have threatened to join the Hague-based International Criminal Court to allow legal action to be taken against Israel, but Abbas did not specify in his address whether he would resort to the ICC.