On Sunday, Iran announced that it had breached the limit on uranium enrichment — fissile purity of 3.67 percent required for electricity generation — detailed in the 2015 nuclear deal with the United States and other international powers. It has threatened to go further.

President Hassan Rouhani had said on Wednesday that Iran would enrich uranium to “whatever levels it needs.” The Trump administration had responded that it would continue its “maximum pressure” policy of stringent economic sanctions until Iran “ends its nuclear ambitions and its malign behavior.”

As citizens of the United States and Iran who have dedicated our lives to the pursuit of peace, we are gravely concerned about escalating tensions between our countries.

The Trump administration’s maximum-pressure policy has brought us to the cliff of an armed confrontation and further inflamed the Gulf region. Although Tehran is far from producing a nuclear weapon, a failed agreement with Washington could lead it to pursue its nuclear program more aggressively. This could set a dangerous global precedent, potentially leading to unregulated proliferation of nuclear weapons.

Washington and Tehran need to de-escalate immediately through maximum diplomacy, with support from other signatories of the nuclear deal,* *and start drafting the terms of an agreement suitable to both.

Iran wants its economic sanctions lifted. The United States wants, at the minimum, an assurance that Iran will not acquire nuclear weapons. Wisdom dictates that the United States and Iran commit to an agreement that addresses these mutual concerns.

On Wednesday, President Rouhani had made it clear that Tehran’s measures were fully reversible: “All of our actions can be returned to the previous condition within one hour.” His statement indicates a willingness to negotiate.

Such openings offer a unique opportunity in conflict resolution and must be invested in immediately through expert and wise diplomatic engagement. The United States can reciprocate by committing to dialogue. Pursuing maximum pressure will only lead to greater “malign behavior”’ on the part of Iran in Iraq, Yemen and Syria.

Too much is at stake and these preventive steps must be taken now. Sunday marked the end of the 60-day ultimatum given by Iran to the remaining signatories of the nuclear deal — China, France, Germany, Russia and Britain — to honor the agreement rejected by the United States. Iran will not back down from further ultimatums.

Inside Iran, intensified conflict with the United States will further embolden Tehran’s harsh stance on human rights defenders, labeling them terrorists and collaborators.

Tehran has already sentenced the human rights lawyer Nasrin Sotoudeh to 38 years and six months in prison and 148 lashes after two unfair trials. Narges Mohammadi, the vice president of the Centre for Human Rights Defenders, has been sentenced to 21 years in prison for her efforts to advance human rights in Iran.

These activists have endured repression for demanding the respect of their fundamental human rights. As tensions with the United States increase, Tehran tightens the screws on human rights defenders to not appear soft on those they accuse of conspiring with the United States and promoting “Western ideals.”

A military confrontation would not only endanger those struggling for freedom and democracy but also further damage the Iranian economy, which is already reeling under American sanctions.

Iranians are deeply affected by a currency that has lost 60 percent of its value since the sanctions were reinstated, and concurrent rising unemployment and living costs. The price of food has skyrocketed, making meat and vegetables unaffordable to ordinary people. Meanwhile those closest to the regime profit from the corruption that is fueled by the sanctions.

Beyond Iran’s borders, a United States-Iran conflict will engulf Israel, Iraq, Saudi Arabia, Yemen and Syria and set the already polarized Persian Gulf region on an even more dangerous trajectory.

Of all the countries in the region, Yemen, which faces the most dire humanitarian crisis, continues to be the battlefield between Iran-backed Houthi rebels and the Saudi- and American-backed coalition. An escalation of tensions between the United States and Iran is endangering the Yemen peace process  and could affect the opening of Red Sea ports and improving aid flows into Yemen.

The costs are also high for Americans. For years, Iran has been preparing to attack American forces in the Middle East as part of its self-defense strategy. Tehran possesses an agile and sophisticated missile force and is well equipped to challenge American interests and its allies in the region. Ordinary citizens of Iran, Yemen and the United States­ — most of whom are women and children — would pay the highest cost of this avoidable conflict.

It is time to bring sanity back to Washington and Tehran and commit to a citizen-centered, maximum-diplomacy approach that protects the fragile equilibrium between our countries. The call for peace in the region has never been more pressing, the stakes never so high.

First published in The New York Times. Cartoon by R.J. Matson.

Shirin Ebadi, an Iranian, received the 2003 Nobel Peace Prize for her efforts to promote human rights in her country. Jody Williams, an American, received the 1997 Nobel Peace Prize for her work to ban antipersonnel land mines.