(CNN) -- U.N. Secretary-General Ban Ki-moon said the world body is unable to determine whether Israelis and Palestinians have done enough to investigate allegations that both sides committed war crimes during last year's war in the Gaza Strip.
Ban outlined the steps taken by both sides in a report to the U.N. General Assembly on Thursday, but found them inconclusive.
"As such, no determination can be made on the implementation of the resolution by the parties concerned," Ban said.
Israelis and Palestinians had till Friday to fulfill a U.N. demand for credible and transparent inquiries into civilian casualties.
The U.N. Human Rights Council released a 575-page report in September that was authored by noted South African judge Richard Goldstone. It concluded that both sides had committed war crimes during the three-week conflict, in which about 1,400 Palestinians and 13 Israelis died.
At the time, Israeli Defense Minister Ehud Barak called the Goldstone report "distorted, false and irresponsible."
Israel handed over a 46-page response to the United Nations on Sunday, outlining the steps it has taken to investigate charges of wrongdoing by its military during the operation, aimed at stopping militant rocket fire from Gaza into Israel.
Israel says it faced "asymmetric conflicts" and blamed "militants operating from within and behind civilian areas" for placing civilians at risk.
The Israeli military has "launched investigations into 150 separate incidents, including 36 criminal investigations opened thus far," according to the report.
"Israel is committed to ensuring that every such incident is fully and fairly investigated, to ensure that lessons can be learned and that, if justified, criminal or disciplinary proceedings initiated," the report says. "To this end, the IDF (Israeli Defense Forces) policy requires that every allegation of wrongdoing be investigated, irrespective of its source."
Israel's response did not mention whether the Jewish state will conduct an independent, non-military investigation of the charges leveled in the Goldstone report, though it has become a source of heated debate in Israel. A chorus of human rights organizations and politicians has called for a more credible examination to be carried out.
For its part, the West Bank-based Palestinian Authority said it had created a commission to look into allegations of abuses, but made clear that it did not view potential wrongdoing on the Palestinian side as seriously as any acts by Israel.
"There is absolutely no symmetry or proportionality between the occupying Power and the occupied people," wrote Riyad Mansour, Palestinian observer to the United Nations.
In Gaza, the ruling Hamas movement this week released a 20-page summary of the steps it has taken to investigate wrongdoing, contending it had prevented militants from rocketing Israeli civilians and that any examples to the contrary were a result of mistaken fire.
It was a claim quickly dismissed by human rights organizations and Israel.
"Hamas can spin the story and deny the evidence, but hundreds of rockets rained down on civilian areas in Israel where no military installations were located," Joe Stork, deputy Middle East director at Human Rights Watch said in a statement. "Hamas leaders at the time indicated they were intending to harm civilians."
The Goldstone report could be referred to the U.N. Security Council for action and ultimately to the International Criminal Court. Both moves are considered unlikely, because the United States, a strong Israeli ally, is a member of the council and would likely veto any any attempt to bring up war crimes charges.
The International Criminal Court at The Hague, Netherlands, is a permanent, treaty-based tribunal dealing with the most serious crimes against humanity. It is an independent court that is not part of the United Nations. It is funded primarily by nations, but also receives contributions from governments, corporations and individuals.