Will the ceasefire between Iran and the United States continue to hold 7 days from today?

TL;DR

I estimate a 77% chance that the U.S.–Iran ceasefire is still in effect on Sunday, June 28, 2026. The June 17 MOU, active Switzerland talks, and continued Hormuz traffic make a clear ceasefire breakdown less likely than the headlines imply. The main NO path is a Lebanon or Hormuz incident that becomes direct U.S.–Iran fire, not a planned decision by either capital to restart the war this week.

Context

The forecast date is Sunday, June 21, 2026, so the resolution date is Sunday, June 28, 2026. A ceasefire is in effect today because the U.S. and Iran signed a June 17 memorandum that declares an immediate end to military operations, starts a 60-day negotiation period, requires the U.S. to begin lifting the naval blockade, and requires Iran to use best efforts for toll-free safe commercial passage through Hormuz for 60 days (Axios MOU text, Jun. 17, AP, Jun. 17).

The ceasefire is also under acute stress. On June 20, Iran said it was closing the Strait of Hormuz because of Israel’s campaign in Lebanon and alleged U.S. noncompliance; on June 21, AP and Axios still described U.S.–Iran talks in Switzerland as active, with Hormuz, Lebanon deconfliction, the MOU, and the nuclear file on the agenda (AP, Jun. 20, AP, Jun. 21, Axios, Jun. 21). Under this question’s rules, that stress is not enough for NO unless it becomes widely reported renewed sustained or large-scale direct U.S.–Iran hostilities, or an official end to the ceasefire.

Evidence

The historical backbone points to high short-run survival, but it is not a clean base rate. The ETH/PRIO Civil Conflict CeaseFire dataset covers more than 2,200 ceasefires in civil conflicts from 1989 to 2020; among failed nationwide ceasefires, the median duration was 65 days to a 25-battle-death threshold and 193 days to a 100-battle-death threshold (ETH/PRIO dataset, Clayton et al., Journal of Conflict Resolution). A rough exponential conversion gives 7-day failure risks of about 7% and 2.5%, respectively. I raise that sharply because this is a recent interstate maritime war with repeated violations and direct U.S.–Iran strikes.

This ceasefire’s own history is a better guide. On May 7, CENTCOM said Iran launched missiles, drones, and small boats as three U.S. destroyers transited Hormuz; the U.S. intercepted threats and struck Iranian launch, command, and ISR nodes (CENTCOM, May 7). On June 5, CENTCOM said Iran fired seven ballistic missiles toward Kuwait and Bahrain after the U.S. shot down four Iranian attack drones near Hormuz; U.S. forces then struck Iranian coastal radar sites (CENTCOM, Jun. 5). On June 9–10, CENTCOM reported U.S. strikes after Iran downed a U.S. Army Apache and then additional strikes on Iranian surveillance, communications, and air-defense sites (CENTCOM, Jun. 9, CENTCOM, Jun. 10). These incidents show that the raw weekly chance of direct fire is high. They also show that even serious exchanges have not automatically been treated as the ceasefire’s formal end.

Country-level conflict data show de-escalation from the March peak, while Lebanon remains a live spoiler. The table below uses ACLED/HDX country-month political-violence aggregates, not actor-coded U.S.–Iran events; units are monthly events and reported fatalities, coverage is July 2025 through partial June 2026, and the vintage is June 21, 2026 (ACLED data portal).

The maritime evidence is mixed but better than a literal reading of Iran’s closure statement. IMF PortWatch daily chokepoint data for the Strait of Hormuz, accessed June 21, had 74 June observations across 2024, 2025, and June 1–14, 2026; the 2026 series was lagged and ended before the June 17 MOU, so it measures the pre-MOU standstill rather than the latest reopening (IMF PortWatch).

The fresher reports point to a managed reopening, not normality. AP reported that major shipowners began moving through Hormuz after the interim agreement, with Kpler seeing 6 verified crossings on June 17 and 11 on June 18, while the main central route still had an estimated 80 mines to clear (AP, Jun. 18). CENTCOM said 55 merchant ships transited on June 20 carrying more than 17 million barrels of oil, and AP reported on June 21 that U.S. Energy Secretary Chris Wright said 67 ships had gone through in the prior 24 hours via a U.S.-opened southern channel (CENTCOM, Jun. 20, AP, Jun. 21). JMIC lowered the Hormuz threat level from critical to moderate after the MOU but still warned about mines, naval presence, congestion, and VHF hailing; Steamship Mutual called the reopening cautious and managed rather than a return to normal operations (USNI News, Jun. 18, Steamship Mutual, Jun. 19).

The diplomatic evidence is the strongest YES signal. The MOU gives both sides a face-saving 60-day process, immediate economic stakes, and time to defer the hardest nuclear questions; the draft text includes oil waivers, asset-release mechanisms, sanctions negotiations, and a future monitoring mechanism (Axios MOU text, Jun. 17, Reuters via Investing.com, Jun. 15). On June 21, Axios reported marathon talks into Sunday night and said officials discussed MOU implementation, Lebanon deconfliction, Hormuz, and the nuclear deal; a U.S. diplomat said the sides made good progress on keeping the strait open (Axios, Jun. 21). The negative signal is that AP also reported Trump threatening to hit Iran over Hezbollah and Iran warning it was prepared to respond, which makes the next week unusually brittle (AP, Jun. 21).

My calculation used four lenses. The generic ceasefire/status lens gives 83% YES after starting from high 7-day ceasefire survival and cutting hard for this case. The recent-incident lens gives 76% YES: about 4.5 serious direct-hostility clusters from early April to mid-June imply a raw weekly incident risk near 37%, but the June 17 MOU, current talks, and the resolution rule’s high threshold cut the relevant NO risk to the low 20s. The Hormuz/Lebanon weak-signal lens gives 70% YES because mines, closure rhetoric, and Israel-Hezbollah fighting are the main failure channels. The actor-incentive lens gives 82% YES because both governments gain more from preserving the MOU for one more week than from restarting open war. Weighting those lenses 20%, 35%, 25%, and 20% gives 77%, with a small upward nudge for the late-June-21 report that talks were still making progress.

What's non-obvious

The closure headline is less decisive than it looks. Iran can declare Hormuz closed as leverage while still allowing enough escorted or southern-channel traffic to avoid forcing an immediate U.S. strike. The operational evidence as of June 21 is not a full closure: CENTCOM reported 55 ships on June 20, AP reported 67 in the prior 24 hours on June 21, and negotiators kept meeting in Switzerland (CENTCOM, Jun. 20, AP, Jun. 21, Axios, Jun. 21).

The resolution threshold also matters. Lebanon fighting, Israeli strikes, Hezbollah attacks, Iranian threats, toll disputes, sanctions fights, mines, cyberattacks, and minor skirmishes are bad for the deal but do not by themselves resolve this question NO. They matter only if they produce clear, widely reported renewed direct U.S.–Iran hostilities or an official declaration that the ceasefire has ended.

Limitations

The biggest gap is real-time maritime truth. PortWatch is useful but lagged through June 14 in the data available on June 21; the key reopening and reclosure claims happened from June 17 to June 21, so the freshest ship-count evidence comes from CENTCOM, AP, Kpler, and Lloyd’s List reporting rather than a single audited public vessel-by-vessel series (IMF PortWatch, AP, Jun. 18, CENTCOM, Jun. 20).

The second gap is classification. A single drone interception, missile launch, or U.S. self-defense strike could be reported as a violation, a defensive incident, or a restart of hostilities. I treat isolated incidents as not enough for NO unless AP, Reuters, BBC, the Washington Post, the New York Times, or comparable outlets describe them as ending the ceasefire.

The third gap is command intent. Public behavior suggests both Washington and Tehran want to keep the 60-day process alive, but IRGC rules of engagement, U.S. strike thresholds, Israeli decisions in Lebanon, and Hezbollah behavior are not transparent. Those hidden thresholds are why I stay well below 85% despite the short 7-day horizon.