GENEVA, Feb 24 (Robert Evans - Reuters) - United Nations human rights chief Navi Pillay defended on Wednesday the controversial Goldstone investigation into Israel's 2008-2009 military assault in Gaza, saying both its methods and conclusions were sound.

The report by a team headed by South African jurist Richard Goldstone was issued last September and found that both the Israeli army and Islamist group Hamas, which controls Gaza, were guilty of war crimes in the conflict but focused more on Israel.

Israel, which refused to cooperate with Goldstone, has condemned the report as distorted and biased and rejected the war crimes allegations. Hamas denied its fighters committed war crimes but has said it regrets Israeli civilian deaths.

Pillay said UN rights missions like Goldstone's were vital for the pursuit of truth, despite attacks by governments and other parties seeking to distract attention from the findings.

'These vehement arguments tried to shift the focus away from the soundness of the methodology and findings of the mission to plunge the debate into the quick sands of the highly partisan politics of the Middle East conflict,' Pillay said in a speech prepared for delivery.

The Goldstone mission 'succeeded in placing the acute need for accountability on the international community's agenda,' compelling the sides to take note of the documented facts and the calls for justice from all victims, she said.

More than 1,400 Palestinians and 13 Israelis died in the 3-week conflict after Israel launched its operation in what it said was a bid to halt Hamas rocket fire on its towns near Gaza.

The Goldstone report called on both sides to carry out credible investigations of their own, saying that if they failed, the question should be referred to the International Criminal Court in The Hague.

But UN Secretary-General Ban Ki-moon earlier this month cast doubt on the credibility of the investigations by the Israelis and the Palestinian Authority, which has no control over Gaza.