Ban opened a special meeting of the United Nations General Assembly with an appeal for a lasting peace as a 72-hour ceasefire between Israel and Hamas was holding for a second day.
"The senseless cycle of suffering in Gaza and the West Bank, as well as in Israel must end," he told the 193-nation assembly.
After three wars in Gaza in six years, the UN secretary general warned that the world's patience with the Israelis and the Palestinians was being tested.
"We will build again but this must be the last time -- to rebuild. This must stop now."
Four weeks of fighting in the Gaza Strip has killed 1,875 Palestinians and 67 Israelis, with nearly half of Gaza's 1.8 million people driven from their homes.
UN Middle East envoy Robert Serry said the destruction and death toll from the latest fighting was worse than the 2008-2009 conflict.
The UN General Assembly was convened at the request of Arab countries, who have criticized the Security Council for failing to adopt a strongly-worded resolution to press Israel and Hamas to stop.
The document has yet to come up for a vote.
The 15-member Council adopted a statement on July 27 calling for a ceasefire and expressing support for Egypt's mediation efforts after the United States dropped reservations that such a text would single out Israel.
