NEW DELHI -- Israel and Hamas have agreed to a humanitarian cease-fire in Gaza to start Friday morning for 72 hours, although Secretary of State John Kerry cautioned that the lull in violence did not guarantee an end to the conflict.

"This is not a time for congratulations or joy or anything except a serious determination -- a focus by everybody to try to figure out the road ahead," Kerry said in New Delhi, where he was meeting with Indian officials. "This is a respite. It is a moment of opportunity, not an end."

The U.S. and the United Nations announced the cease-fire in a joint statement.

Israeli and Palestinian delegations were expected to travel immediately to Cairo for talks with the Egyptian government aimed at reaching an end to the conflict, now more than three weeks old.

"It is up to the parties -- all of them -- to take advantage of this moment," Kerry said. "There are no guarantees. This is a difficult, complicated issue."

During the cease-fire, Kerry said Israel will be able to continue its defence operations to destroy tunnels that are behind its territorial lines. The Palestinians will be able to receive food, medicine and humanitarian assistance, bury their dead, treat the wounded and travel to their homes. The time also will be used to make repairs to water and energy systems.

"We hope this moment can be grabbed by both parties, but no one can force them to do that," Kerry said.

The joint statement said the U.S. and U.N. had gotten assurances that all parties to the conflict in Gaza had agreed to an unconditional cease-fire during which there would be negotiations on a more durable truce.

"Israel has to live without terror and tunnels and rockets and sirens going on through the day," Kerry said. "Palestinians have to be able to live freely and share in the rest of the world and live a life that is different from the one they have long suffered."

The Palestinian delegation is expected to include members of Hamas, which the United States and Israel consider a terrorist organization and cannot be negotiated with directly. So if the Israelis and Palestinians meet face to face, the Hamas members will not participate in those talks.

The Egyptians will be the go-between for all of this and will help co-ordinate, a senior State Department official said, speaking on condition of anonymity because the official wasn't allowed to discuss the issue publicly by name.

U.N. spokesman Stephane Dujarric said the cease-fire announcement was the result of Secretary-General Ban Ki-moon's trip recent trip to the region "but also 48 hours of extremely active diplomacy at all levels from the secretary-general to his senior advisers talking to key regional players as well as Robert Serry, who is in Jerusalem, talking to his counterparts."

Serry is the U.N. special co-ordinator for the Middle East peace process.

U.S. Mideast envoy Frank Lowenstein and others were expected to go to Egypt for the Egyptian-mediated talks in Cairo.

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Associated Press writers Edith M. Lederer at the United Nations and Mathew Lee and Deb Riechmann in Washington contributed to this report.