(CNN) Iran's second pledge to breach the terms of the landmark nuclear deal was light on detail, but heavier in consequence.

And it pretty much encapsulated the mood music of the Persian Gulf right now: a move that permits great, inflammatory rhetoric, but changes little in practice.

Tehran declared Sunday that it would enrich uranium past the limit of 3.67% set by the deal. In the past few months Iran had suggested that this might mean 3.7%, while on Saturday they mentioned as much as 5%. But it conspicuously left out any number from the announcement Sunday.

It was the sequel to last week's declaration that they would enrich more low-grade uranium past the stockpile limit of 300kg (660 pounds) set out by the deal.

Iran has vowed to increase its uranium enrichment beyond the 3.67% limit set out in the 2015 deal.

That earlier move was purely symbolic: there's little you can do with tons of 3.67% enriched uranium bar power an older pressurized water reactor for a little while, and it has no use for a bomb at all. Enriching uranium to 3.7% is equally as useless, and 5% isn't much help either.

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