The deal reportedly addresses Israel's repeated assertation that cement and other materials could be used to rebuild Hamas tunnels, by setting up a UN monitoring mechanism of the imports. The monitoring agreement must "get up and running without delay," said Serry.
He described the destruction in Gaza as "truly shocking," AFP reports with some 18,000 houses flattened or severely damaged while 65,000 Palestinians remain in UN-run shelters and 100,000 are homeless.
Mr. Serry appealed for the re-opening of border crossing points, to allow the delivery of materials, emphasizing that quick action on reconstruction would provide a "signal of hope to the people of Gaza."
A donor conference for Gaza reconstruction is scheduled for Oct. 12, to be held in Egypt and supported by Norway. However, the UN Security Council has been unable to agree on a draft resolution for full implementation of the Gaza truce, for which further talks are scheduled in September.
"The crisis in Gaza is far from over and the window of opportunity to address critical needs and stabilize the situation is short," Serry warned.
The envoy appealed for action to "change fundamentally the dynamics in Gaza," warning that "if we do not, Gaza could implode -- or, yet again, explode -- possibly with a new and even more devastating round of violence."
Following weeks of Egyptian-brokered negotiations, Israel and Hamas agreed to halt their fire in Gaza on Aug. 26 after 50 days, their deadliest confrontation in years.
The indirect talks are set to resume mid-September to discuss longer-term issues.
UN diplomats, however, are concerned about Israeli and Palestinian commitment to peace talks, with one Security Council member saying that the sides appeared to be drifting toward a "cold peace."
The council separately has been unable to agree on a draft resolution to shore up the Gaza truce.