Iran-U.S. feud: What is 'uranium enrichment' and why does it matter?
By Zhou Wenjia

Iranian President Hassan Rouhani said on Wednesday Iran is ready to restart a critical aspect of its uranium enrichment program.

Rouhani said Iran will begin developing centrifuges, as early as Friday. It marks the third step in breaking the 2015 nuclear deal with world powers.

Rouhani's statement comes as the U.S. hits Iran with new sanctions.

U.S. President Donald Trump imposed sanctions on Iran's space agency and two affiliates this week. The State Department said this is the first time the U.S. has put sanctions on Iran's civilian space agency for its alleged involvement in ballistic missile development.

The sanctions included banning Iranian entities in the U.S. and barring U.S. citizens from doing business with them. Rouhani responded by calling the sanctions invalid.

Also this week, the Trump administration imposed sanctions on a shipping network that Iran uses to sell oil.

Rouhani uses the third step to give European powers pressure as he earlier said he will give European countries two more months to save the pact as France earlier offers Iran about fifteen-billion US dollars in credit until the end of the year, if Tehran returns to full compliance.

The major concern over Iran's nuclear program often revolves around its capability to enrich uranium. So what does this mean? The video gives a quick explanation.