Iran said it would begin to increase its enrichment of uranium—a step toward potentially making a nuclear weapon—as the country presses Europe for relief from crippling U.S. sanctions.

President Hassan Rouhani said that starting Sunday, Iran would take steps to enrich uranium to levels beyond the limit set in the 2015 deal to curb Tehran’s nuclear program. His remarks were a repeat of previous threats by Iranian officials that, if realized, would mark Iran’s second deliberate violation of the multilateral accord.

“On [July 7] our enrichment level will no longer be 3.67%. We will set this commitment aside,” Mr. Rouhani said Wednesday in comments carried by state television. Iran, which maintains that its nuclear program is peaceful, hasn’t said to what level it would enrich the uranium.

Iran has repeatedly threatened to increase enrichment if European nations don’t provide some relief from U.S. sanctions and work harder to keep the accord alive. The Trump administration unilaterally withdrew from the agreement last year.

On Twitter Wednesday, President Trump said: “Iran has just issued a New Warning. Rouhani says that they will Enrich Uranium to ‘any amount we want’ if there is no new Nuclear Deal. Be careful with the threats, Iran. They can come back to bite you like nobody has been bitten before!”