Iran’s role in the new U.S.-led coalition of the willing against ISIS has been something of a mystery since the group came together in the fall. Iran clearly agrees with the U.S. and its allies on the need to confront ISIS and maintain the integrity of what’s left of the Iraqi state, but given the ongoing dispute over Iran’s nuclear program and the deep disagreement over what to do about Syrian President Bashar al-Assad, neither side is going to talk openly about cooperation.

There have been reports for months of Iranian advisers helping coordinate anti-ISIS efforts on the ground in Iraq. Tehran has also been supporting the Syrian government since the beginning of the civil war, but the Iranian military doesn’t appear to have taken direct action against ISIS. Until now … maybe.

U.S. officials said today that they believe Iran carried out airstrikes against Islamic State targets in Iraq 10 days ago, near the Iranian border. Iranian officials are denying that the strikes took place.

Footage from Al-Jazeera shows what experts say is an F-4 fighter jet attacking the targets in Iraq’s Diyala province. Iran and Turkey are the only countries in the region that use F-4s, and given the proximity to Iranian territory and Turkey’s reluctance to get involved in the fight against ISIS, Iran is the most likely culprit. Nonetheless, the Iranian government is sticking with its story. A senior official tells Reuters, “Iran has never been involved in any air strikes against Daesh [the preferred term for ISIS in the region] targets in Iraq. Any cooperation in such strikes with America is also out of question for Iran.”

As the BBC explains, the F-4 is an American-made plane, and several hundred were sold to Iran before the 1979 revolution. The planes saw frequent combat during the Iran-Iraq War of the 1980s, but in recent years, U.S. sanctions have made it hard to find spare parts for the aging planes. A story in the Greek media earlier this year suggested that Israeli arms dealers may have been illegally supplying Iran with spare F-4 parts.

So in case you’re keeping score at home, Iran, America’s sworn enemy, is denying American accusations that it is cooperating with America to attack their common enemy using American planes, which, thanks to American sanctions, are being illegally maintained, possibly with the assistance possibly with the assistance of Israelis. Got that?