VIENNA — Iran plans to enrich uranium up to 20% at its underground Fordow nuclear facility, international inspectors said Saturday, pushing its program a technical step away from weapons-grade levels as it increases pressure on the West over its tattered atomic deal.

The International Atomic Energy Agency acknowledged Iran had informed its inspectors of the decision after news leaked overnight Friday.

The enrichment plan exceeds regulations set by the 2015 Joint Comprehensive Plan of Action known as the Iran nuclear deal, as first reported by Reuters. Iran has previously suggested this increase could be a possibility.

The nuclear deal includes regulations that Iran cannot enrich uranium past 3.67% and that it specifically cannot conduct any enrichment at Fordow, which is located beneath a mountain near the city of Qom.

The move comes amid heightened tensions between Iran and the US in the waning days of the administration of President Donald Trump, who unilaterally withdrew America from Tehran's nuclear deal in 2018.

The decision comes after parliament passed a bill, later approved by a constitutional watchdog, aimed at hiking enrichment to pressure Europe into providing sanctions relief. It also serves as pressure ahead of the inauguration of President-elect Joe Biden, who has said he's willing to reenter the nuclear deal.

“Iran has informed the agency that in order to comply with a legal act recently passed by the country’s parliament, the Atomic Energy Organization of Iran intends to produce low-enriched uranium ... up to 20 percent at the Fordow Fuel Enrichment Plant,” the IAEA said in a statement.

Iran has already breached parts of the agreement since the Trump administration withdrew in 2018, including increasing enrichment of uranium to 4.5%. Bringing enrichment to 20% would be the highest the country has gone since the agreement was established in 2015. In order to manufacture a nuclear weapon, it must hit 90%.

France, Germany and UK brand Iran’s nuclear plans ‘deeply worrying’

The IAEA added Iran did not say when it planned to boost enrichment, though the agency “has inspectors present in Iran on a 24/7 basis and they have regular access to Fordow.”

Mikhail Ulyanov, Russia's permanent representative to the Vienna-based IAEA, wrote on Twitter on Friday that Tehran planned to resume enrichment up to 20% after a Wall Street Journal journalist broke the news.

IRNA later reported Ulyanov's comments, linking the decision to the parliament bill aimed at restarting higher enrichment at Iran's underground Fordow facility. It also offered no timeframe for starting the higher enrichment.

Iran separately has begun construction on a new site at Fordow, according to satellite photos obtained by the Associated Press in December. — Agencies