WASHINGTON -- The Bush Administration on Thursday began to seek ways to expand Iran's apparently pivotal role in sparing the life of hostage Joseph J. Cicippio into a resolution of the five-year-old hostage crisis.

Although relieved U.S. officials still are trying to piece together the sequence of events that led to the "freezing" of the death threat against Cicippio, national security analysts said they have learned that key leaders in Lebanon of the radical Shiite Muslim movement Hezbollah were summoned Thursday to the Iranian Embassy in Damascus, Syria, and told that Iran wanted Cicippio's life spared.

After that meeting, Cicippio's Shiite captors announced that the deadline for executing him had been extended four hours. Later in the day, they said they were "freezing" the death sentence indefinitely, citing "intervention by some states and parties that were asked by the United States to mediate."

Iran Role Could Be Opening

Iran's involvement "could be" an opening toward eventually getting some or all of the hostages released, as well as toward a possible long-term improvement in relations with Iran, one Administration official said.

"It's one small step," this official said. "The optimists among us would like to believe (that) it might be enough to lead to more improvement."

In an official statement, White House spokesman Marlin Fitzwater said: "We express our appreciation to all those who have been thus far trying to help." But he went on to say that lifting the immediate death sentence for Cicippio "still does not answer our continuing concern for release of all hostages."

In addition to Iran, U.S. officials also were crediting Syrian Presi-dent Hafez Assad, whose nation also has influence over radical Islamic groups in Lebanon, with playing a key role in forestalling the crisis.

State Department spokeswoman Margaret Tutwiler publicly acknowledged Syria's efforts Thursday, saying that Damascus has assured U.S. officials of its intention to be "helpful." Reflecting the Administration's continued questions about Iran's intentions, Tutwiler offered a more guarded assessment of Tehran's role.

"At this time we have no reason to believe that Iran is not dealing with this matter in a serious way," she said.

The announcement that the death threat against Cicippio had been suspended came at the end of an almost frenzied search by American officials for diplomatic channels that could be used to influence the radical Shiite factions that hold Cicippio and seven other U.S. hostages in Lebanon.

Bush Called Leaders

President Bush personally called several Middle Eastern leaders, including Algerian President Chadli Bendjedid, Saudi Arabia's King Fahd, Jordan's King Hussein and Morocco's King Hassan II as well as Pope John Paul II and leaders in Turkey, Britain and West Germany. State Department officials also sent repeated messages to Iran through the Swiss, Japanese and Syrian embassies in Tehran, officials said.

While they awaited signs of a response, the government's leading experts on Iran met at the State Department on Thursday for what one official called a "brainstorming session" about what to do next.

Options prepared by the Pentagon included possible military action. Asked about a report that Bush was prepared to order an air strike on an eastern Lebanon militant camp in Baalbek if Cicippio had been killed, Secretary of State James A. Baker III late Thursday said a full range of contingencies was held open. Focusing on one now, he said in a broadcast interview, would be "very hypothetical and very speculative." White House spokesman Marlin Fitzwater said earlier in the day that no decision had been made on any particular action.

In the end, analysts said, the announcement on freezing the death sentence may have been at least partly tied to Hashemi Rafsanjani's inauguration Thursday as Iran's new president.

U.S. officials say they believe that Rafsanjani may be interested in improving relations with the United States as he seeks to right Iran's war-battered economy and that he saw the hostage gesture as a worthwhile step.

Now, Administration officials say, they are looking for ways to continue this momentum, fearing that if it is lost, the hostages may again become pawns in internal Iranian power struggles.

The officials cautioned that, while Iran and Syria both have influence over the radical groups that hold the hostages, that influence is limited. The small Lebanese factions of the Hezbollah movement control the situation "like a faucet," one senior official said. "The threat can be renewed in five minutes."