Israel will push forward with its offensive in the Gaza Strip until it "completely destroys" Hamas, Israel's ambassador to the United Nations, Gabriela Shalev, said Monday, saying that the operation will continue as long as necessary to reach that goal. Shalev also played down international criticism of the offensive and ruled out a return to the terms of a recent cease-fire with Hamas that collapsed in violence over the weekend. Shalev expressed regret for civilian deaths in Gaza, but said Hamas was responsible for the bloodshed by operating in residential areas and using civilians as "human shields." "We are very sorry, and really I say it as a mother, as a grandmother ... to speak of children and of women being killed," she said. But "it's only the Hamas to blame." Shalev refused to discuss Israel's war strategy, but said the operation would continue "as long as it takes to dismantle Hamas completely." "The main goal is to destroy completely this terrorist gang, which makes people on both sides of the border, in Gaza and in Israel, suffer daily," she said. Shalev would not say whether that would mean toppling the Hamas government, but she said Israel would like to see its negotiating partner, Palestinian Authority President Mahmoud Abbas, regain control of Gaza. Shalev said Israel would not accept a return to the terms of the recent truce, which was repeatedly marred by sporadic Palestinian rocket fire. She noted that Hamas simply used the lull to restock its arsenal. "What we want this time is a commitment and assurances that Hamas will not shoot any rockets and will not fire on Israeli citizens any more," she said. Shalev said Israel is "concerned" about the international criticism, and has tried to send messages to the Arab world that it wants peace. "But first of all, we have the right to defend ourselves and we have the duty to protect our citizens. This comes before the understanding, which we hope to receive, of the international community," she said. Shalev said Israel's rival politicians have come together in unity over the offensive, and noted that when US President-elect Barack Obama visited Israel last summer, he voiced support for the country's right to defend itself.