The agreement will provide American technical assistance, as well as monitors, to crack down on the network of tunnels through which Hamas moves components for rockets and missiles through the Sinai Peninsula into Gaza. The composition of the monitoring force was not yet clear, as Israeli and American diplomats were still working out final details, a senior American official said, speaking on condition of anonymity.

Ms. Rice said ending the smuggling of weapons from countries like Iran was one of the conditions for a cease-fire and that European allies including Britain, Germany and France were likely to join in the monitoring effort.

But she said the agreement was only supportive of broader negotiations being carried out by Egypt, and she refused to say when a cease-fire could actually take place and the fighting in Gaza would stop.

“We are doing everything we can to bring it to an end,” she said.

She raised the possibility of donor conferences  possibly led by the Czech Republic and Norway  to deal with the humanitarian conditions in Gaza after a cease-fire and to help rebuild the territory.

“There is much that can be done to bring Gaza out of the dark of Hamas’s reign and into the light of the very good governance the Palestinian Authority can bring,” she said.