Iran has been one of Washington’s chief antagonists for nearly four decades. But a deal to keep Tehran from building nuclear weapons is in sight.

Tehran, though an ugly regime, does not threaten America. The United States is the globe’s greatest military power with the most sophisticated nuclear arsenal and finest conventional force.

Tehran’s leaders are malign actors, but nevertheless have reason to feel insecure. In 1953 Washington helped overthrow the democratically elected prime minister. Presidents George W. Bush and Barack Obama regularly declared military action to be “on the table.”

Israel is concerned over a possible Iranian nuclear weapon, but when asked in 2011 whether Iran would drop a nuke on Israel, former Defense Minister Ehud Barak responded “Not on us and not on any other neighbor.” Israeli Defense Force’s Lt.-Gen. Benny Gantz observed: “I think the Iranian leadership is comprised of very rational people.” Who recognize Israel’s overwhelming retaliatory capacity.

Washington’s ally the Shah started the Iranian program. Tehran’s motive, noted former Mossad head and national security adviser Efraim Halevy, “is not the confrontation with Israel, but the desire to restore to Iran the greatness of which it was long deprived.”

Tehran does not appear to have an active weapons program. Instead, it is hedging, putting off any decision.

Negotiations began to move seriously after the 2013 election of Hassan Rouhani as Iran’s president. The interim Joint Plan of Action limited Iran’s nuclear program and increased international surveillance.

More needs to be done. But only negotiation is likely to yield additional restrictions and oversight.

For years hawks erroneously predicted that Iran was about to build nuclear weapons. Instead, negotiations have reduced Tehran’s “breakout” capacity, the time necessary to enrich enough uranium to make one bomb. Before the JPOA Iran’s breakout time was a month or so. The U.S. hopes to push that up to a year.

The basic dispute is whether the West demands complete termination of Iran’s nuclear activities or agrees to program limits backed by intrusive oversight.

Iran is unlikely to surrender: there is broad domestic support for Iran’s nuclear program. In contrast, a more limited pact would discourage development of a nuclear bomb.

Uranium enrichment may be the most important area of dispute since it is as much political as technical. A compromise deal likely is the best the West can expect. Having endured years of escalating penalties, Tehran isn’t likely to accept less. U.S. military action would set the stage for another extended Middle Eastern disaster.

Compromise also is the best that Tehran can expect. Iran needs an agreement to meet its economic and security needs. The alternative is persistent economic crisis, geopolitical isolation, and military threat.

There are other issues between the West and Iran, including the latter’s regional role. But resolving the nuclear controversy would improve the chances of addressing other disputes.

Nevertheless, negotiation critics promise a better deal if the administration stands firm. Hard-line Republican senators believe Iran should essentially surrender.

Alas, Tehran did not respond to prior pressure by crawling to Washington. Instead, Tehran added centrifuges and increased reprocessing capabilities. As I warn on Forbes online, “Demanding capitulation would risk restarting Iranian efforts, ending enhanced inspections, and encouraging Tehran to follow North Korea in leaving the NPT entirely.”

Having blown up the negotiations, the U.S. then might find war the only alternative to a nuclear Iran. A military strike likely would only delay rather than stop the program. The prospects for democracy in Iran would die, while the impact in the Middle East could be catastrophic.

Thus, negotiations remain the only realistic option to prevent an Iranian bomb. They also could dramatically reduce tensions in the Middle East.

Tehran is an ugly regime, but that only makes a reasonable and enforceable nuclear agreement more critical. For the people of America and Iran, failure is not an option.