According to the International Atomic Energy Agency (IAEA), Iran is approaching a significant hurdle in the production of nuclear weapons-grade material. According to the latest IAEA report from Vienna published on Monday, there were an estimated 3,809.3 kilograms of enriched uranium in the country’s stocks in mid-May. The Islamic Republic enriched 43.1 kilograms of uranium to a purity of 60 percent, according to the organization’s report, which was available to the German Press Agency. Around 50 kilograms would be enough for a nuclear weapon if the material were enriched a little higher to 90 percent, said a senior diplomat who has been monitoring Iran’s nuclear program for a long time.

The IAEA quarterly report on Iran was prepared against the background of the negotiations to save the nuclear pact with Iran. The talks are on the brink because Washington and Tehran cannot agree on which US sanctions will be lifted.

A renewed restriction of the Iranian nuclear program, however, has already been largely negotiated. Western diplomats have been warning for months that the restoration of the 2015 nuclear deal is becoming increasingly unlikely the further Iran pushes uranium enrichment in particular.

Tehran has always emphasized that it does not seek nuclear weapons, but uses uranium only for nuclear power plants and for scientific and industrial purposes. However, the IAEA has not yet been able to confirm this.

Contrary to an agreement, Tehran has still not explained why the IAEA has detected traces of uranium at several sites not declared as official nuclear sites, according to another report released by the agency on Monday. Iran “has not provided any technically credible explanations,” it said.