An Iranian security official in protective clothing walks through a uranium conversion facility in 2005. Iran says it is now enriching uranium above the limit set in the 2015 nuclear deal.

Vahid Salemi/AP

Updated on Monday at 12:40 p.m. ET

Iran has crossed another line set in the 2015 nuclear deal between it and major world powers.

According to state media, Iran has begun enriching uranium above levels enshrined in the agreement. The move sends a signal that Iran is losing patience with a deal that has not provided the economic relief promised, more than a year after the United States withdrew from the agreement.

By Monday, Iran had reached levels of around 4.5% enrichment, Behrouz Kamalvandi, the spokesman for the Atomic Energy Organization of Iran, told the semiofficial Fars news agency. He warned that Iran could go as high…