Iranian President Hassan Rouhani inspects an honour guard during his ceremonial reception in New Delhi, India.Adnan Abidi / Reuters

During the Obama years, Saudi Arabia and its Middle East allies were enraged by Washington’s perceived indifference to their security concerns over Iran. They couldn’t seem to convince the president that Tehran’s ambitions posed the greatest security threat to the region.

Then came Donald Trump, who seemed eager to adopt their view of Iran as the single most malignant threat to the region—the world, even. Tuesday, Trump delivered, announcing that the United States would pull out of the landmark nuclear deal negotiated by the Obama administration and five other world powers, and reimpose harsh sanctions that badly damaged Iran’s economy.

But Riyadh, along with the six-member Gulf Cooperation Council and its Arab allies, may find the Trump administration’s scuttling of the deal, known as the Joint Comprehensive Plan of Action, only initiates a fresh period of uncertainty and instability in the region. That instability may drive up oil prices, much to the delight of Saudi Arabia. But it could also raise new security, diplomatic, and economic concerns. If the deal fully collapses, Iran’s neighbors who opposed it may also one day be challenged by a country  with a nuclear program that is no longer under the 24-hour scrutiny of international inspectors.

In his address Tuesday afternoon, Trump cited Saudi Arabia and regional concerns that Iran has “caused havoc throughout the Middle East and beyond” in the years since the nuclear deal was forged, and said this was one reason for withdrawing from the nuclear deal and re-imposing heavy sanctions on Tehran. Saudi Arabia’s official news agency issued a lengthy statement, attempting to explain its support for Trump’s move. The United Arab Emirates and Bahrain also announced their support. “I think Trump gets top grades for this one,” Ali Shihabi, the founder of the Arabia Foundation, a think tank close to the Saudi leadership, told me. “I think everyone will be very satisfied with this move because it puts the Iranians under the microscope.”

But Gulf leaders may be disappointed by the actions of a fickle president with a history of making splashy announcements and failing to follow through. The Gulf states may be anticipating more from the deal’s demise than the United States can deliver.

“The view of most GCC security professionals is that the West was suckered by the Iranians, who we don't understand, and cavalierly disregarded legitimate GCC security considerations,” said David Des Roches, an associate professor at the Near East South Asia Center for Strategic Studies, a think tank of the Department of Defense. “But they probably expect more follow-up than we are willing to provide.”

The Saudi rivalry with Iran dates back decades, to before the 1979 overthrow of  Iran’s monarchy in a revolution led by Shia Muslim clerics and their followers. Saudi Arabia’s newly anointed Crown Prince Mohammed bin Salman has blamed post-revolutionary Iran for many of the region’s ills, including the influence of ultra-conservative Wahhabi clergy in his own kingdom.

He and his mentor, Crown Prince Mohammed bin Zayed Al Nahyan of the United Arab Emirates, have spent months actively lobbying Trump to take a harder stance against Iran. Abandoning the nuclear deal is one part of that effort.

“In a way, their opposition to the deal is out of spite to the way they felt they were ignored by the Obama administration,” Emile Hokayem, a Middle East specialist at the International Institute for Strategic Studies in London, told me.

Saudis don’t like the Iran deal, but they don’t regard it in and of itself as a threat. Rather they see Iran’s broader ambitions as the problem.“The key thing is this naivete that drove the Obama administration--this view that we’re dealing with a responsible reliable party created a lot of concern,” Shihabi said. “Ending the sanctions not only sent the wrong signals but allowed the regime to continue funding its nefarious activities.”

Hokayem, who speaks regularly to officials and diplomats in the Arab world, suspected any satisfaction would be tempered by the Trump administration’s incoherent policies in Iraq and Syria, two geopolitical battlegrounds contested by Iran and Saudi Arabia.“The cooler heads in Riyadh and Abu Dhabi understand that you’re in no better position and possibly a worse position,” said Hokayem. “There’s no absolutely no clarity for what comes next. There’s no sense of commitment by the Trump administration to anything sustainable in the region.”

But Shihabi said Trump’s tough position on Iran,  including his pledge to institute “the highest level of economic sanction,” would be difficult to walk back. “He has now taken a very public position and a very clear decision,” Shihabi said.

Israel is concerned about Iran’s nuclear program itself, which poses a potential challenge to Israel’s presumed nuclear arsenal. But Saudi Arabia and its allies, including the UAE, Egypt, and even Morocco, which recently cut formal ties with Iran and accused its ally Hezbollah of supporting rebels in the Western Sahara, are more concerned about Iran’s meddling on the ground: its support for ideologically fervent militias in Iraq, Syria, Lebanon, and Yemen; its alleged shipments of rockets that are now regularly launched by Yemen’s Houthi rebels at Saudi Arabia; its political domination of Arab capitals from Sanaa to Beirut.

“Riyadh was particularly concerned that the deal would embolden Iran’s regional activities, providing them with more cash to support allies in Syria, Lebanon, Iraq and elsewhere,” Elizabeth Dickinson, a Gulf-based researcher for the International Crisis Group, an international conflict-resolution organization, said.

To many Saudis, those worries have become reality. In the more than two years since the deal was implemented, Iran’s proxies have picked up more battlefield successes, Tehran’s missile program has expanded, and its political influence has increased, even as its nuclear program has been put into check.

But experts warn that scuttling the nuclear deal might actually further embolden Iran. “If the U.S. were to renege on its commitments in the deal, Iran will almost certainly react in some manner,” Dickinson said. “Axing the nuclear deal may offer a moment of catharsis, but be ultimately counter-productive.”

Even worse: the possibility Tehran could use any U.S. withdrawal from the deal to slowly ramp up its nuclear program if the deal fully falls apart and Europe fails to meet Iranian demands for economic assurances. While Trump said the JCPOA would lead to an nuclear arms race, Iran’s ramping up of enrichment is a more likely spark to such a crisis. In a speech shortly after Trump’s announcement, Iranian president Hassan Rouhani vowed to stay in the deal, but also said he had ordered officials to prepare for a possible “industrial-scale enrichment” in case Europe and others fail to take steps to ameliorate the U.S. withdrawal.

“The Iranians will probably then say the deal is worthless which means that the Iranians return to a nuclear program,” said James Dorsey, a Middle East specialist at the S. Rajaratnam School of International Studies in Singapore. “Which means that you get a nuclear race in the Middle East.”

Wendy Sherman, a former U.S. diplomat who helped negotiate the nuclear deal, told reporters in a conference call on Tuesday: “Iran with a nuclear weapon would be able to project even more power in the region.”

For the Gulf, there are other potential repercussions of the nuclear deal’s demise. Oil prices have been rising ahead of an anticipated new crisis in Middle East, helping finance bin Salman’s outsized domestic ambitions. But if prices rise too high, U.S. shale producers will have an incentive to enter the market, ultimately driving down prices. “The higher prices go, the faster the marginal shale operators can return to the market,” said Matt Dabrowski, a Chicago-based political-risk consultant. “Most analysts I speak to see oil prices dropping into next year, even in a sanctions scenario. Ironically or not, the beneficiaries will be Western shale producers, who will have another chance to eat into Saudi Arabia's market share.”

While bin Salman and bin Zayed may be on board with Trump’s plan to scuttle the nuclear deal, not all of the Gulf players are in agreement. Dubai, one of the seven princedoms that make up the UAE, vies with China as Iran’s biggest trading partner, and would be hard-pressed to further Iran’s isolation at a time when its own economy is in a somewhat perilous state. Qatar, which has been blockaded by Saudi Arabia over its independent-minded foreign policy and alleged support for militant groups, may drift further into the orbit of Tehran. Oman and Kuwait, already seeking to play a mediating role between Saudi Arabia and Qatar and Saudi Arabia and Iran, may come under more pressure to choose sides. Turkey, which plays an increasingly important role in Gulf affairs and investment, this morning condemned the U.S. withdrawal from the nuclear deal, putting it opposite Riyadh and Abu Dhabi.

“At the moment the Gulf is already totally torn apart,” Camille Lons, a Gulf specialist at the European Council for Foreign Affairs, said. “It will definitely pull the GCC even further apart.”