TEL AVIV, Israel — The viability of a U.S.-backed proposal to wind down the 8-month-long war in Gaza was cast into doubt on Monday after Israeli Prime Minister Benjamin Netanyahu said he would only be willing to agree to a “partial” cease-fire deal that would not end the war, comments that sparked an uproar from families of hostages held by Hamas. [time-brightcove not-tgx=”true”] In an interview broadcast late Sunday on Israeli Channel 14, a conservative, pro-Netanyahu station, the Israeli leader said he was “prepared to make a partial deal — this is no secret — that will return to us some of the people,” referring to the roughly 120 hostages still held in the Gaza Strip.