Iran's stock of uranium close to weapons grade has jumped since December, two reports by the U.N. nuclear watchdog said on Wednesday.

Iran has substantially expanded production of highly enriched uranium since December, further increasing its stockpile of near-weapons-grade material, according to a person familiar with a report prepared for next week’s meeting of the International Atomic Energy Agency’s board of governors.

Iran has accelerated its production of near weapons-grade uranium as tensions between Tehran and Washington rise after the election of U.S. President Donald Trump, a report by the United Nations’ nuclear watchdog seen by The Associated Press on Wednesday showed.