Israel must investigate allegations that its army violated international law during its three-week war against Hamas militants in the Gaza Strip, the new U.S. envoy to the United Nations said on Thursday.

"We expect Israel will meet its international obligations to investigate and we also call upon all members of the international community to refrain from politicizing these important issues," Ambassador Susan Rice said in her debut speech before the U.N. Security Council.

Rice said that Hamas had been guilty of violating international law "through its rocket attacks against Israeli civilians in southern Israel and the use of civilian facilities to provide protection for its terrorist attacks."

"There have also been numerous allegations made against Israel some of which are deliberately designed to inflame," she told the council during a meeting on international humanitarian law.

Some 1,300 Palestinians, including at least 700 civilians, were killed during Israel's Gaza offensive, according to the Hamas-run Health Ministry in the territory. Israel put its losses at 10 soldiers and three civilians.

During the campaign, Israel fired on several U.N. installations in Gaza, including schools, where hundreds of Palestinians had been seeking shelter from the fighting. Israel rejects allegations that its army was guilty of war crimes.

U.N. Secretary-General Ban Ki-moon has said there would also be a U.N. investigation of the deadly attacks on United Nations sites in the Gaza Strip.

Rice made it clear that the administration of U.S. President Barack Obama had a very different view of the role of the United Nations from George W. Bush's government, whose officials were often suspicious of the world body and occasionally spoke of it with disdain.

She said Obama's long-term goals included enhancing global peace and security, fighting terrorism and the proliferation of weapons of mass destruction, dealing with climate change, alleviating poverty and improving respect for human rights worldwide.

"The United Nations is indispensable for advancing these goals and making our world a better, safer place," she said.

She also hinted that Obama had a different attitude towards The Hague-based International Criminal Court, the world's first permanent war crimes tribunal.

President Bill Clinton's administration had signed the ICC treaty, which was never ratified by Congress. Bush later rejected the idea of ever joining the court.

"The International Criminal Court, which has started its first trial this week, looks to become an important and credible instrument for trying to hold accountable the senior leadership responsible for atrocities committed in the Congo, Uganda and Darfur," Rice said.