JERUSALEM, AUG. 17 -- Israeli authorities, saying they are concerned about signs of growing instability in Jordan and other Arab countries, have concluded that the United States must act quickly in the Persian Gulf crisis or face the risk that turmoil will spread in the Arab world.

Although the Bush administration has succeeded in fashioning an alliance against Iraq that includes Saudi Arabia, Egypt, Syria and Morocco, Israeli analysts believe the Arab governments could face potentially serious unrest at home if the crisis drags on and Iraqi President Saddam Hussein continues his appeals to Arab nationalist sentiment.

In particular, senior Israeli officials say there is growing alarm in the government over the situation in neighboring Jordan, where King Hussein appears unable to break his ties to Iraq or resist the mounting pro-Saddam sentiment in his population. "The king seems to us to have lost control," said a high official. The official said Israel was worried because the Jordanian army has been placed on high alert.

The volatility of Jordan, which threatens to extend the gulf crisis to Israel's borders, and signs of growing tension in the Israeli-occupied West Bank and Gaza Strip as well as in Syria, have caused senior Israeli officials to conclude that the United States can probably not afford to wait out a trade embargo of Iraq that might take months to yield results.

Instead, official analysts here have concluded that the United States' best option may lie in staging a single, massive air and missile strike against Iraq in the near future, a knock-out blow that would render Saddam incapable of offensive military activity and perhaps break the morale of his army. According to Israel's intelligence assessment, U.S. forces in the gulf should be strong enough to deliver such a blow by the end of another week to 10 days of deployments.

"Time is working against the United States and all of us in this situation," said a senior official, who asked not to be named. "What is clear is that if the situation continues to develop as it has, the troubles may spread well beyond the gulf, to Jordan and eventually to us."

The Israeli evaluation of the crisis reflects the importance the government here places on breaking the power of Saddam and the skepticism with which it views the budding U.S. alliance with Arab regimes such as Saudi Arabia and Syria. Israeli officials warned Washington of Iraq's military buildup nearly two weeks before the invasion of Kuwait on Aug. 2.

The idea of a preemptive air strike against Iraq is in keeping with a strategy that led Israel to carry out its own bombing raid in 1981 on an Iraqi nuclear complex that allegedly was intended for weapons production.

Israeli concerns have been focused on Jordan since the gulf crisis began. The government of Prime Minister Yitzhak Shamir fears the destabilization of King Hussein, a leader with whom Israel has grown comfortable, and is determined to prevent Iraq from establishing a military presence in the country. Repeatedly in recent days, Israeli leaders have stressed that the movement of any Iraqi force into Jordan -- even a single brigade -- would be considered an act of war by Israel.

In a briefing for several Western journalists today, a senior military source said Israel had been particularly disturbed by events of recent days in Jordan. "The air smells of war from this side of the border," he said. "The king and his regime are blowing the winds of war."

The military source said Israel had noticed that the Jordanian army has been put on high alert and added that "they are doing a huge number of strange things." Among them, he said, was the recruitment of up to 80,000 Jordanians for service in the Iraqi army, the staging of an air raid alert in Amman and the encouragement of panic buying by the public. "Is there no one behind this?" he asked.

"They are preparing the Jordanian army and the Jordanian citizen for a possible war in the very near future," the military source said. "Maybe they know something we don't know. Maybe they are playing together with Iraq."

Both military and government sources said Israel had concluded that King Hussein was in a critically weak position and was probably no longer capable of acting independently of Saddam. "The situation is deteriorating," said a government official. "From our point of view anything is possible because the king's state of mind is pressured, to say the least."

The pro-Saddam demonstrations in Jordan have been echoed in the neighboring West Bank, where Israeli troops have been breaking up marches by youths shouting militant pro-Iraqi slogans every day this week. Although the disturbances remain mild compared to the worst periods of the intifada, the 32-month-old Arab rebellion in the occupied territories, Israeli security sources fear the mounting emotions could eventually spark a new explosion of unrest here.

Israeli sources say they also have picked up signs of tension in Syria, whose President Hafez Assad reversed 20 years of hard-line resistance to Western aims in the Middle East by joining the embargo and multinational force against Iraq. In recent days, sources said, posters praising Saddam and lambasting Syria's alignment have appeared in the cities of Hama and Homs, fundamentalist Moslem strongholds, as well as in the Druze villages of the Golan Heights.

Syria, the sources said, appears to be trying to minimize its commitment to Egypt and the United States for the deployment of forces. According to Israeli intelligence, less than a full brigade of Syrian troops has arrived in Saudi Arabia and a similarly small force has been moved toward the Syrian-Iraqi border. "They are as far to the rear as they can get," an official said.

The official added that Israel believes King Hassan of Morocco is also under pressure. "He is despondent and unsure of what he is doing, because of the price he may pay with his own people," the official said.

During the course of the crisis, Israeli officials and some politicians have expressed concern that the United States will not have the resolve to move forcefully against Saddam if sanctions appear to be failing. But one senior official today said that in the government's view "it now seems that {President} Bush is determined to take action, even if the bureaucrats try and stop him."

Although military ground action against Iraq's huge army would be infeasible in the near future, Israeli analysts believe the United States could deal a crushing blow to Saddam by massing all of its air power for a coordinated attack. Although it would not dislodge Iraqi infantry from its defensive positions in Kuwait, officials said, such an attack could serve to destroy Iraq's air force and air defenses, its missile batteries and other key infrastructure.

"You have to do it once, massively and efficiently," one official said. "You don't want to have to have a second air strike -- the objective must be to leave Saddam without the capacity to strike back."