TEHRAN   -   Tehran has sped up the countdown to its breaching the nuclear deal, announcing it will break the uranium stockpile limit set in the deal in the next 10 days.

The country’s atomic agency also said Tehran could from 7 July start the process of enriching uranium up to 20%, closer to weapons-grade levels.

The announcement by Behrouz Kamalvandi, the spokesman for the Iranian Atomic Energy Authority, puts more pressure on Europe to come up with new terms for Iran’s 2015 nuclear deal.

The EU last week agreed an unpublished timetable of its own with Iran to help ease trade between Tehran and European nations, but it is not clear whether the measures will come quickly enough or be sufficient to persuade Iran to rethink its strategy of chipping away at the deal. Iran says it is acting after Donald Trump unilaterally pulled out of the deal a year ago and Europe then proved itself incapable of protecting its private-sector firms from the threat of US secondary sanctions if they tried to trade with Iran. US sanctions have brought down Iran oil exports to 400,000 barrels a day, well below the levels needed to fund government spending.

Washington and the UK have blamed attacks on oil tankers in the Gulf of Oman last week on Iran. Tehran has denied any involvement and described them as a false flag operation. The EU has yet to allocate blame.

Iran’s army chief Major General Mohammad Hossein Baqeri said on Monday that if Iran ever decided to block the export of oil from the Gulf, it would do so openly, without resorting to deception or covert operations, unlike the “terrorist and deceptive” US. In a briefing on Monday, Kamalvandi accused Europeans of “killing time”, adding: “If this condition continues, there will be no deal.”

Under the terms of the nuclear agreement, Iran can keep a stockpile of no more than 300kg (660lbs) of low-enriched uranium. Kamalvandi said given Iran’s recent decision to quadruple its production of low-enriched uranium, it would pass the 300kg limit on 27 July. The United Nations’ nuclear watchdog, the International Atomic Energy Agency, said last month Iran still remained within its stockpile limits. The agency reported that Iran’s stockpile of enriched uranium was 174.1kg in late May. Iran said the breach was likely partly because the US had placed sanctions on Iranian exports of uranium.

Heavy water supplies at the Arak water reactor will exceed a 130-ton limit within the next two and a half months if the country does not find a client to buy heavy water byproducts.

Kamalvandi said additionally that Iran needed 5% enrichment for its nuclear power plant in the southern Iranian port of Bushehr and 20% enrichment for a Tehran research reactor. His formulation did not amount to a firm commitment to reach 20% levels.

The nuclear deal had limited Iran to enriching uranium only to 3.67%, which is enough for power plants and peaceful purposes.

Tehran first set the 7 July deadline before it would boost enrichment six weeks ago. Kamalvandi reiterated that stance, saying Tehran would increase uranium enrichment levels “based on the country’s needs”.

Enriching a supply of uranium means boosting its concentration of the type of uranium that can power a nuclear reaction. That type, or isotope, is called U-235. Enrichment means stripping away atoms of another isotope, U-238.

When uranium is mined it typically has about 140 atoms of this unwanted isotope for every atom of U-235. Refining it to a purity of 3.67%, the level allowed by the nuclear deal, means using centrifuges to remove 114 unwanted atoms of U-238 for every atom of U-235.

Boosting its purity to 20% means removing 22 more unwanted isotopes per atom of U-235, while going from there to 90% purity means removing just four more per atom of U-235. Ninety per cent is considered weapons-grade material.

In an attempt to dramatise Iran’s decision, Kamalvandi spoke to Iranian journalists in a news conference at the country’s Arak heavy water nuclear reactor. Such reactors produce plutonium that can be used in nuclear weapons. Iran, under the nuclear deal, had reconfigured the facility to address western concerns on that issue.

However, Kamalvandi said the country could rebuild the facility with Chinese help to make it produce plutonium. He also said Iran would continue to allow the UN to inspect its nuclear facilities.

In Brussels on Monday, EU foreign ministers said they were still looking for more information on who might be behind the incident involving the tankers last week.

The German foreign minister, Heiko Maas, said US and British intelligence needed to be compared with other information from allies. “We have to be very careful,” he said.

The EU foreign policy chief, Federica Mogherini, said it was not the time to jump to action without proper information. “The maximum restraint and wisdom should be applied,” she said.