While the world has been focusing on Donald Trump’s summits with NATO and Russia’s Vladimir Putin, tensions are escalating dangerously between Washington and Tehran. On Sunday, Iranian President Hassan Rouhani cautioned his U.S. counterpart not to “play with the lion’s tail.” Using the harshest words of his presidency, Rouhani told a gathering of Iranian diplomats that “America should know peace with Iran is the mother of all peace, and war with Iran is the mother of all wars.” Trump responded by tweeting that Iran should “NEVER EVER THREATEN THE UNITED STATES AGAIN.”

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In recent days Rouhani has warned that Iran may block Persian Gulf oil shipments if its own exports are stopped; Iran’s Supreme Leader Ayatollah Khamenei has proclaimed Trump’s policies a declaration of war and Revolutionary Guards Commander Mohammad Ali Jafari threatened that "we will make the enemy understand that either all can use the Strait of Hormuz or no one." In response, U.S. Central Command spokesman Bill Urban stated that the U.S. Navy stood "ready to ensure the freedom of navigation and the free flow of commerce wherever international law allows.”

Such drastic escalation would not only mean the death of the multinational Iran nuclear deal known formally as the Joint Comprehensive Plan of Action – from which Trump withdrew in May – but the start of a U.S.-Iran war and a broader conflict that would make ongoing regional crises pale in comparison. Any U.S. effort to block Iranian oil exports would be a violation of U.N. Security Council Resolution 2231 endorsing the nuclear deal. But if Tehran were to respond in kind by blocking oil shipments through the Strait of Hormuz, Europe, Russia and China will drop their support for the JCPOA and join the United States to pass a punitive U.N. Security Council resolution against Iran. Yet in spite of the rising rhetoric, there are still reasonable options that could avert the risk of catastrophic conflict.

One possibility is direct negotiations between Washington and Tehran. Trump has indicated he believes his hard line will prompt Iran to seek a "bigger deal" with Washington, telling a press briefing at this month’s NATO summit that Tehran “at some point will call me and ask for a deal, and we'll make a deal." However, Trump needs to understand that his current strategy forecloses opportunities for diplomatic compromise because, as Rouhani’s “mother of all wars” statement shows, Iran’s leaders are unlikely to accept the humiliation – and the blow to national pride – of a complete surrender to Trump's threats and pressure.

Another option is that the JCPOA continues without the United States. Iran’s leaders have said they are prepared to continue implementing the accord’s commitments with its remaining signatories – China, Russia, France, Germany, the U.K. and the EU – on the condition that the Trump administration does not force those countries to join Washington in breaking the agreement.

It’s true that the non-U.S. signatories will be unable to fully compensate Tehran financially for the re-imposition of U.S. sanctions. But one consequence of the Trump administration’s hardline approach is an increased sense of national unity in Iran – and that could prompt Iranian domestic political factions to put aside their differences and adopt a united front against the foreign threat.

The recent Revolutionary Guards' support of the Rouhani administration – with Major General Qassem Soleimani, the commander of the Iranian Revolutionary Guards' Quds Force writing to Rouhani praising his tougher stance against Washington – is an indication to the international community of the internal pushback against the White House. “We’ve become more united than before, threats bring us together,” Rouhani said on Sunday.

Rouhani has made powerful statements indicating that he is willing to use this unity to make major decisions on solving chronic economic problems such as corruption, inflation, unemployment, privatization, and smuggling. Iran needs these structural reforms to get rid of chronic imbalances and the dependence on oil revenues that have made it so vulnerable to sanctions, along with an overhaul of its banking system to restore international trust in its financial institutions. If these succeed in improving Iran’s economy, it will make it easier for Iran to remain in the JCPOA.

European leaders also may be willing to make some concessions to Iran in the political and security domains to compensate for the loss of the benefits it was due under the accord. While Rouhani has expressed doubts over Europe’s package of economic incentives to preserve the agreement, Iranian Foreign Minister Javad Zarif is continuing to work on securing financial, banking, and energy commitments from his counterparts from China, Russia, Germany, France, and the U.K.

It’s crucial that these nations continue not only to maintain the JCPOA, but to work with Iran to manage the regional crises in Syria and Yemen – thereby removing Trump’s linkage of his withdrawal from the JCPOA with what he called “Iran’s destabilizing activities” and “menacing activity across the Middle East.”

Recent negotiations between Iran and four European states over the Yemeni crisis have been characterized as positive and constructive. If Russia and China joined this diplomatic process, these seven countries can take a peace proposal to the U.N. Security Council. This plan can be based on a ceasefire, humanitarian aid, national dialogue, free elections, and inclusive government. Resolving the Yemeni crisis will end the world's worst humanitarian crisis.

In Syria, too, there is an opportunity for action. Although hostilities continue, Islamic State has been ousted from its territory in the country and support from Moscow and Tehran has ensured that Bashar al-Assad remains in control. Now is the time for Russia and Iran, along with Turkey, to present a plan for a comprehensive peace in Syria to the U.N. Security Council and for Europe and China to support it. The JCPOA represents a model for crisis resolution through diplomacy; its death will mean killing the hope that negotiations can resolve other regional crises. Europe, China, Russia, and Iran all have the responsibility to confront unilateralism; protecting the JCPOA is the first step. Through cooperation, these states can play a decisive role in facilitating the peaceful resolution of regional crises, defeat terrorism, establish a new model for regional conflict resolution – and perhaps preserve the Iran nuclear deal itself.