It marks the first major departure from the unravelling agreement a year after the US unilaterally withdrew from the accord.
The announcement by Iran's foreign minister Mohammad Javad Zarif, and later confirmation by the UN nuclear watchdog, puts new pressure on European nations trying to save the deal amid President Donald Trump's campaign targeting Tehran.
Iran is also threatening to raise its uranium enrichment closer to weapons-grade levels on July 7 if Europe fails to offer a new deal.
Although Mr Trump pulled back from air strikes targeting Iran after the US drone was shot down, Washington has rushed an aircraft carrier strike group, nuclear-capable B-52 bombers and thousands of additional troops to the region.
That has raised fears that a miscalculation or further incidents could push the two sides into an armed conflict, 40 years after the Islamic Revolution and the takeover of the US embassy in Tehran.