After months of US opposition, the Iran arms embargo at the UN has expired, and despite the US opposition, UN officials are uniform in agreement that it actually has expired. Don’t tell that to the Trump Administration though, as they insist it’s still in place.
Reflecting US promises to enforce the non-existent embargo themselves, Secretary of State Mike Pompeo threatened to impose US sanctions on any nations that sell arms to Iran, or offer them training or services.
That’s been the US position since they failed to extend the embargo, but it’s not clear it will actually do anything, as the nations most likely to provide Iran with arms and services, Russia and China, will almost certainly ignore US threats the same way they do on everything else Iran-related.
Iranian officials don’t expect a huge rush to buy arms anyhow, as a decade of embargos has made them self-sufficient in a lot of things. Still, Russia and China can offer some better versions of equipment, or at a better price than Iran can make them themselves, and there is no real legal obstacle to that anymore.
The fact that the US opposes, or indeed “forbids” such sales is likely to ensure that some happen just to spite them, with Russia in particular very clear that they intended to make sales to Iran once the legal restriction was lifted.