The terror group that’s taken over major portions of Iraq and Syria won’t be content with roiling those two countries, senior Obama administration officials told Senators in a classified briefing this week. The Islamic State of Iraq and al-Sham (ISIS) also has its eyes on Jordan; in fact, its jihadists are already Tweeting out photos and messages claiming a key southern town in Jordan already belongs to them.

An ISIS attack on Jordan could make an already complex conflict nightmarishly tangled, the officials added in their briefing. If the Jordanians are seriously threatened by ISIS, they would almost certainly try to enlist Israel and the United States into the war now engulfing the Middle East.

“The concern was that Jordan could not repel a full assault from ISIS on its own at this point,” said one senator, who spoke on condition of anonymity. Another Senate staff member said the U.S. officials who briefed the members responded to the question of what Jordan’s leaders would do if they faced a military onslaught from ISIS by saying: “They will ask Israel and the United States for as much help as they can get.”

If ISIS were to draw Israel into the regional conflict it would make the region’s strange politics even stranger. In Iraq and Syria, Israel’s arch nemesis, Iran, is fighting ISIS. Israel, on the other hand, has used its air force from time to time to bomb Hezbollah positions in Syria and Lebanon, the Lebanese militia aligned with Iran. If Israel were to fight against ISIS in Jordan, it would become a de facto ally of Iran, a regime dedicated to its destruction.

But Jordan is also an important ally for Israel. It is one of two countries (along with Egypt) to have a peace treaty with the Jewish state. Jordanian security forces help patrol the east bank of the Jordan River that borders Israel and both countries share intelligence about terrorist groups in the region.

For now the one thing Iran and Israel do agree on is that U.S. intervention in Iraq is risky. Khamenei has told Obama to just stay out. Netanyahu was more subtle, warning that Obama should not promise Iran anything in the nuclear negotiations that might entice its cooperation in Iraq. His advice was for Obama to weaken both sides.

But behind the scenes, Israeli diplomats have told their American counterparts that Israel would be prepared to take military action to save the Hashemite Kingdom.

Thomas Sanderson, the co-director for transnational threats at the Center for Strategic and International Studies, said Israel and the United States view the survival of the Jordanian monarchy as a paramount national security objective.

“I think Israel and the United States would identify a substantial threat to Jordan as a threat to themselves and would offer all appropriate assets to the Jordanians,” he said.

Sanderson, who is a former contractor for the Defense Intelligence Agency, said those assets would include air power and intelligence resources, but he stressed that whatever Israel and the United States offered Jordan would be tailored to the kind of threat ISIS posed. “It’s impossible to rule out boots on the ground from Israel or the United States, but that is the least likely scenario. Amman would have to be under siege for that to happen,” he said.

While the U.S. intelligence community estimates that ISIS only has 3,000 to 5,000 fighters who are full members of the organization, the group is nonetheless a potent force. In its military campaigns in Iraq and Syria, ISIS has seized millions of dollars worth of cash and advanced military equipment from bases abandoned by the Iraqi and Syrian armies.

That said, Jordan’s special operations forces are considered by military experts to be professional and competent. The tiny country that borders Syria, Saudi Arabia, Israel and Iraq has survived terrorism, insurrection and regional war since it gained independence in 1946.

A spokeswoman for the Jordanian embassy in Washington, Dana Daoud, said the country’s military and security forces were fully capable of meeting the ISIS threat. “We are in full control of our borders and our Jordanian Armed Forces are being very vigilant,” she said. “We have taken all the precautionary measures. So far, we have not detected any abnormal movement. however, if anything threatens our security or gets near our borders it will face the full strength of our Jordanian Armed Forces.” Earlier this week, Jordan closed a major border crossing with Iraq.

Rep. Adam Schiff, a Democrat who serves on the House Permanent Select Committee on Intelligence and is a co-chair of the Congressional Friends of Jordan Caucus, said in an interview that the threat from ISIS could draw the United States into the conflict. But he also said he had more confidence in Jordan’s military than he did in Iraq’s.

“I don’t think there is any sense that the rank and file Jordanian forces will melt away the way the Iraqis did,” he said. “It’s a different context in Jordan. If the need arises, they will provide more than a match for ISIS.”

In the last two decades Jordan has made a strategic decision to ally closely with America. Today the country is one of America’s closest partners in counter-terrorism. After U.S. forces lost access to Iraqi military bases in 2011, Jordan emerged as the most important base for the CIA in the region. The CIA, for example, trains Syrian rebels from positions inside Jordan. On Thursday, the White House asked Congress to authorize an additional $500 million for military training and equipment for those opposition forces.

At times, the close partnership with Jordan has resulted in tragedy. A triple agent provided to the CIA by Jordanian intelligence ended up detonating himself and seven other CIA operatives at one of the agency’s outpost in Khost, Afghanistan in 2009.

In the last year, the U.S. military has also positioned batteries of Patriot missiles and a fleet of F-16s inside Jordan along with a contingency of U.S. soldiers known as Centcom-Forward Jordan. That group is led Brig. General Dennis McKean, one of whose missions is to help plan for Jordan’s defense in the midst of the chaos that has enflamed the region.

“Jordan is a very close partner to the United States, and we have shared their concerns about violence spilling across the border for some time,” said Commander Bill Speaks, a spokesman for the Office of the Secretary of Defense. “We are committed to supporting Jordan’s security and continually assess the situation and how best to support our friends in the region.”

One of those threats today is coming from the southern Jordanian city of Ma’an. Aymenn Jawad Al-Tamimi, a Shillman-Ginsburg Fellow at the Middle East Forum who specializes in jihadist groups in Syria and Iraq, said, “Jordan is a part of the Sham, the Levant states that also include Lebanon, that ISIS aims to control as part of its near-term ambitions. But Jordan is a more viable target for them than Lebanon at the moment and the signs of local support, like in Ma’an, will embolden them.”

Even before the ISIS offensive in Iraq, supporters of the group had tweeted maps showing the city of Ma’an in southern Jordan, as part of a regional Caliphate. Last week, a photo from Ma’an showed ISIS supporters holding a banner declaring the city "the Fallujah of Jordan," comparing it to the city in western Iraq that fell to ISIS in January.

With the threat to Jordan rising, Secretary of State John Kerry met Thursday with Jordan’s Foreign Minister Nasser Judeh in Paris in a group that also included Saudi Foreign Minister Saud al-Faisal and Emirati Foreign Minister Abdullah bin Zayed.

“The reason that he pulled them together is because, one, the threat of [ISIS] is not just to Iraq. It’s to the region,” said a senior administration official.

But Kerry and the Arab foreign ministers didn’t discuss any specifics of how to work together to fight against ISIS, the official added. They talked generally about the situation on the ground, the formation of the new Iraqi government, and their shared frustration with Iraq’s prime minister, Nouri al-Maliki, but not about direct security cooperation.

“As a sort of front-line state in the fight against [ISIS], Jordan is certainly one of the countries that we are directly referencing when we talk about the potential of a threat,” the official said. “That said, the current focus of [ISIS] activity is inside Iraq, is inside Syria, and to the extent that [ISIS] has sort of designs on other places, that was not directly discussed today.”

The threat to Jordan is on the minds of many lawmakers though in Washington. Schiff said that if the Kingdom of Jordan were in danger of falling, “We would be prepared to provide a whole different level of material support than anything we are talking about in Iraq.” He added, “I still don’t think there are many foreseeable circumstances for American boots on the ground, nor do I think the Jordanians would ask for them. But the willingness to provide greater material support, greater intelligence support, and the willingness to stand behind the Jordanian government is an order of magnitude greater than what we have done for Iraq.”

Perhaps that’s one of the reasons why the senators who emerged from this week’s briefing on ISIS were so grim.

“We have to be concerned no longer simply about what’s happening in Iraq, but the risk it poses to Jordan and other countries in the region as well,” he said. “We need to work closely with our allies in the region, particularly Jordan, to protect them from the growing risk that this poses.”

— with additional reporting by Josh Rogin and Jacob Siegel