Ray Takeyh is a senior fellow at the Council on Foreign Relations.

The great powers are again resuming diplomatic efforts to settle the Iran nuclear issue. Expectations are high, as Iran is now presumed to be ruled by pragmatists who seek to end its isolation. Although much of the recent international focus has been on President Hassan Rouhani and his indefatigable foreign minister, Mohammad Javad Zarif, the critical decisions will be made by Iran’s Supreme National Security Council. The composition of that body and its new leadership say much more than Rouhani’s proclamations do about the direction of Iran’s foreign policy.

The council increasingly is populated by a cohort of hard-liners who have spent much of their career in the military and security services. The head of the council is Ali Shamkhani, a hardened member of the Revolutionary Guards and former minister of defense who has played a critical role in all of Iran’s important national security decisions since the inception of the theocracy. Shamkhani’s deputy is a shadowy Revolutionary Guards officer, Ali Husseini-Tash, who for decades has been involved in Iran’s nuclear deliberations.

This new cast of characters was critical of former president Mahmoud Ahmadinejad and his unwise provocations and rhetorical excess. They sense that as Iran increases its power, it behooves Tehran to present itself as a more reasonable actor, imposing limits on expressions of its influence and acceding to certain global norms. For instance, Iran has condemned the use of chemical weapons in Syria and has declared its readiness to deal constructively with the nuclear issue.

Despite their interest in diplomacy and embrace of more tempered language, Shamkhani and his advisers believe that Iran must claim its hegemonic role. With the displacement of Iran’s historical enemies in Afghanistan and Iraq, and the unsteady political transitions in the Arab world, they sense that it is a propitious time for the Islamic Republic to claim the mantle of regional leadership. Tehran has been offered a rare opportunity to emerge as the predominant power of the Persian Gulf and a pivotal state in the Middle East. It is immaterial whether its assessment of regional trends is correct, as such perceptions condition its approach to international politics.

The newly empowered conservatives at the council’s helm also believe that Iran needs a nuclear capability to enhance its influence. As Husseini-Tash noted in 2006 during a rare public appearance, “The nuclear program is an opportunity for us to make endeavors to acquire a strategic position and consolidate our national identity.” But they also recognize the importance of offering confidence-building measures to an incredulous international community. All of this is not to suggest that Iran is inclined to suspend its nuclear program or relinquish the critical components of such a program. They are, however, more open to dialogue than the Ahmadinejad government was. Moreover, they stress that a reasonable Iran can assuage U.S. concerns about its nuclear development without having to abandon the program.

Despite its softened rhetoric, the new Iranian regime can be expected to continue asserting its nuclear “rights” and to press its advantages in a contested Middle East. The Islamic Republic plans to remain an important backer of the Assad dynasty in Syria, a benefactor of Hezbollah and a supporter of Palestinian rejectionist groups. It will persist in its repressive tactics at home and continue to deny the people of Iran fundamental human rights. This is a government that will seek to negotiate a settlement of the nuclear issue by testing the limits of the great powers’ prohibitions.

Washington need not accede to such Iranian conceptions. The United States and its allies are entering this week’s negotiations in a strong position. Iran’s economy is withering under the combined pressures of sanctions and its own managerial incompetence. The Iranian populace remains disaffected as the bonds between state and society have been largely severed since the Green Revolution of 2009. The European Union is still highly skeptical of Iran, a distrust that Rouhani’s charm offensive has mitigated but not eliminated. Allied diplomats can use as leverage in the forthcoming negotiations the threat of additional sanctions and Israeli military force.

Given the stark realities, it is time for the great powers to have a maximalist approach to diplomacy with Iran. It is too late for more Iranian half-steps and half-measures. Tehran must account for all its illicit nuclear activities and be compelled to make irreversible concessions that permanently degrade its ability to reconstitute its nuclear weapons program at a more convenient time. Anything less would be a lost opportunity.