An understated consequence of the July 2015 Iran nuclear deal was that it represented conflict resolution through a multilateral framework and a step away from forceful US unilateralism. Washington, it seemed, had turned its back on the days of the George W. Bush administration’s seeming indifference to the interests and concerns of other global powers, exemplified most saliently by its military interventions in the Middle East.

The US foreign policy establishment’s narrative of global order has long rested on the United States being the single indispensable global power whose involvement is necessary to solve the world’s great problems. Of course, not all regional and global powers have bought into this, and some are increasingly moving towards asserting themselves as responsible for the maintenance of political and economic order in their respective regions—as evident in initiatives such as Russia’s Eurasian Economic Union or China’s Asian Infrastructure Investment Bank and One Belt One Road project.

The “emerging multipolar order” has been acknowledged by figures such as Henry Kissinger, who has stressed the importance of establishing a global balance between the major powers. President Obama, meanwhile, was cautious of US overstretch and did not hesitate to invoke James Madison’s warning that “no nation could preserve its freedom in the midst of continual warfare.” His negotiating of the Iran deal partly signified an understanding that the key to preserving global peace and security lies in forming a multipolar order in which the United States can accommodate the concerns and interests of other global and regional powers.

The Iran deal was indeed beneficial for all the parties that negotiated it. The United States gained verifiable guarantees that Iran’s nuclear program could not be diverted towards building nuclear weapons; Iran won implicit recognition of its uranium enrichment program and nuclear-fuel-cycle infrastructure, widely acknowledged to be permitted by the nuclear Non-Proliferation Treaty; and Europe, Russia and China avoided another potential conflict on their periphery and gained the opportunity to engage in heightened security and economic cooperation with Iran.

While Donald Trump has promoted a nationalistic foreign policy that has in many ways accelerated the waning of America’s role as the sole arbiter for international order, in the Middle East he has opted for a return to the traditional US approach of maintaining strategic dominance through a system of alliances underpinned by US military, political and economic intervention. To that end, he elected to visit Saudi Arabia and Israel for his first trip abroad as president in May. He decisively aligned with Crown Prince Mohammad bin Salman’s wing of the Saudi royal family and the right-wing Benjamin Netanyahu government in Israel.

Since Trump’s visit to Saudi Arabia and Israel, he has shown himself committed to their visions of a purported rising Iranian threat in the region. Trump now appears set on decertifying Iranian compliance with the nuclear deal in October, per a congressional mandate, despite the U.N. nuclear watchdog’s insistence that Iran is abiding by the deal.

However, if Trump is to succeed in scuttling the agreement and intensifying pressure on Iran, he will need the buy-in of the five other powers that negotiated the deal, namely France, the United Kingdom, Germany, China, and Russia as well as the European Union. Secretary of State Rex Tillerson has reportedly been lobbying the European states to win their acquiescence to renegotiating or supplementing the pact with new limitations on Iran—proposals Iran has categorically opposed.

While European leaders have thus far remained steadfast in their commitment to the nuclear deal, there are signs some may buckle to US pressure to extend the deal’s sunset provisions and add new limitations regarding Iran’s ballistic missile program. Russian President Vladimir Putin appears more unshakable, and recently hosted Iranian Foreign Minister Javad Zarif in Sochi, where the two reiterated that the deal is “non-negotiable.”

A key inflection point for the deal’s fate and its impact on international politics is the September 20^th meeting between the P5+1 world powers and Iran on the sidelines of the U.N. General Assembly, where Tillerson will push for discussion of the “agreement’s flaws.” The response of the other P5+1 powers will be decisive, not just for the fate of the deal but also for the international order.

Other world powers have the option of preserving the deal, which Iran has suggested it will stick to even if the United States were to withdraw. This would require resisting US pressure and challenging potential secondary sanctions on non-US firms doing business with Iran. In doing so, the other powers would demonstrate their capability to arbitrate an issue of major international concern independently of the United States and their readiness to seek balancing leverages when faced with uncompromising and unilateralist US intentions.

If, on the other hand, the other world powers decide to follow the Trump administration’s line and revisit the deal, it would entangle them in a fundamentally aggressive US approach, one that resorts to the use of pressure even after successful diplomacy and increases the likelihood of war. They would also signal acceptance of US unreliability in meeting its agreed-to commitments, emboldening a Trump administration that has already withdrawn from the Trans-Pacific Partnership and Paris Climate Accord.

Above all else, for the rest of the P5+1 powers to accept the Trump administration’s stance on the Iran nuclear deal would indicate their disposition to ceding to US preferences even in the face of a self-avowed “America-first” administration. It would mean that a multipolar world order is still far from reality.

Sina Toossi is a Senior Research Specialist at Princeton University’s Woodrow Wilson School of Public and International Affairs. He tweets @SinaToossi.