Prime Minister Benjamin Netanyahu of Israel defended on Sunday his government’s plan to launch a renewed offensive against Hamas in parts of Gaza, following a wave of international condemnation from traditional allies and critics at home.

The Israeli military was preparing to expand its campaign to central Gaza as well as Gaza City, Mr. Netanyahu told reporters at a news conference in Jerusalem. Hundreds of thousands of Palestinians have sought shelter in those areas, hoping they would be safer.

Mr. Netanyahu’s proposal has drawn fierce criticism from the families of Israeli hostages, who fear their loved ones will be killed in the Israeli assault. The country’s leaders also overruled the objections of Israeli military leaders, who had raised concerns over the exhaustion among their soldiers.