Israeli officials acknowledged they would have to turn their focus toward affecting the outcome of the final negotiations.
Israel is not part of the Geneva talks but remains in close touch with the U.S. and other participants.
Israel feels especially threatened by Iran, given Tehran's repeated references to destroying Israel, its support for hostile militant groups on Israel's borders and its development of long-range missiles.
Israeli President Shimon Peres, a Nobel Peace laureate, expressed cautious optimism that Sunday's deal could change the region.