Iran has resumed the production of 20% enriched uranium at its underground nuclear facility in Fordow, an Iranian government spokesman said Monday. Iranian state media later reported that authorities had seized a South Korean-flagged and arrested its crew, alleging "oil pollution" in the Persian Gulf.

The big picture: The news comes amid heightened U.S. fears of a possible Iranian attack, one year after the assassination of Iranian Gen. Qassem Soleimani. 20% enriched uranium — which is banned under the 2015 nuclear deal — can’t be used for military purposes, but is a step closer to the 90% enrichment needed to build a nuclear bomb.

Driving the news: Last week, Iran notified the International Atomic Energy Agency of its plans to restart production of 20% enriched uranium.

• The Iranians said the move is the result of a new law that passed in the Iranian parliament several weeks ago, which calls for increased enrichment in order to pressure the Europeans to provide sanctions relief.
• The law is also seen as retaliation for the assassination of Iranian chief nuclear scientist Mohsen Fakhrizadeh, which Iran alleges was carried out by Israel.
• The Iranian government spokesman said President Rouhani ordered the launch of 20% enrichment and the gas injection process to begin at the Fordow facility on Monday morning.

What they're saying: "The government has already announced that it considers the law passed by the parliament to be binding and will adhere to it," the Iranian government spokesman said.

• Israeli Prime Minister Benjamin Netanyahu said in a statement that the move is a violation of Iran’s nuclear commitments and proof that Iran wants to continue its military nuclear program. "Israel will not allow Iran to produce nuclear weapons," Netanyahu said.

The big picture: The announcement come less than three weeks before Biden assumes office, and is perceived as an Iranian attempt to pressure the new administration to move quickly toward rejoining the nuclear deal and easing sanctions.

• Biden says he will return to the 2015 deal if Iran returns to compliance, and plans to use it as a platform to negotiate a broader and longer-lasting deal. That would require the U.S. to lift sanctions and Iran to unwind its recent nuclear activities.