LONDON — Iran announced on Monday that it would soon violate a central element of the landmark 2015 nuclear deal, which the United States withdrew from last year, unless it received assurances that Europe will combat punishing American sanctions.

Iran is on track to exceed the deal’s limits on nuclear fuel within days, the country’s Atomic Energy Organization announced. The agency also left the door open to an “unlimited rise” in Tehran’s stockpile of enriched uranium, potentially triggering another flash point with Washington just days after attacks on oil tankers stoked tensions between the two nations.

The move was the country’s latest signal that it will abandon the pact unless other signatories help Iran circumvent economic sanctions imposed by President Trump. The threat seemed aimed primarily at the European signatories, to persuade them to break with Washington and swiftly restore some of the economic benefits of the deal to Tehran.

During a news conference announcing the decision, Behrouz Kamalvandi, a spokesman for the organization, said that Iran might also increase the level of uranium enrichment up to 20 percent for use in its reactors, the Iranian state-run news outlet Press TV reported.