Last week’s preliminary pact to curb Iran’s nuclear ambitions provides an opportunity to resolve a perilous dispute through negotiations rather than warfare. President Obama and Secretary of State John Kerry deserve credit for embracing a diplomatic approach in their dealings with both the world powers represented by the five permanent members of the U.N. Security Council and Germany (the “P5+1”) and with long-isolated Iran itself.

The negotiated results aren’t perfect. Iran will still have nuclear know-how and capacity. But the tentative deal scales back Iran’s ability to weaponize, prolonging the time it would need to achieve a weapon from a matter of months to at least a year, which would give the P5+1 and others time to react to Iranian backsliding.

The initial deal isn’t inked, but among the surprisingly specific and restrictive conditions are limits on the number of Iranian centrifuges and the level of enriched uranium allowed. Most important, a vigorous protocol of inspections will be implemented.

In return, Tehran, long hobbled by severe sanctions that were possible only through multilateral cooperation, will be granted relief if it verifiably complies with the agreement. It’s crucial that the final pact include stringent “snapback” sanctions should Iran cheat. Rightly, U.S. sanctions imposed to punish terrorism, human-rights abuses and ballistic-missile development will remain.

That sends a signal to key, concerned constituencies. Arab allies are understandably alarmed by Iranian aggression and influence in Iraq, Syria, Lebanon and Yemen. Obama has wisely invited Gulf leaders to a summit. He should reassure them that the alliance remains strong and that keeping Iran from developing a weapon is in their security interest.

U.S. policy also seems to favor the proposed Arab League joint military force, and U.S. intelligence is aiding the Saudi-led bombing campaign against Iranian-backed Houthi rebels in Yemen. That conflict is partly playing out as a proxy war between predominantly Persian, Shiite Iran and predominantly Arab, Sunni Saudi Arabia.

Introducing nuclear weapons into this underlying conflict and the broader cauldron of the Mideast could be catastrophic. This agreement could help prevent that. The deal is in Israel’s best interest, too, despite opposition from Prime Minister Benjamin Netanyahu.

Critics should remember that Iran’s considerable concessions are the result of multilateral, not bilateral, negotiations. If the United States spikes the deal in favor of tougher terms, the likelihood is a backfire: The P5+1 unity — and sanctions — would likely unravel. Inspections could be curtailed, or eliminated, and Iran could once again be dangerously close to a nuclear weapon.

The logical sequence could then increase calls for military action in a region already roiling in multiple, complex conflicts. Diplomacy designed to prevent this may have delivered a breakthrough, which should be given a chance to be finalized.