Iran intends to inform the United Nations nuclear watchdog that it has started to increase its uranium enrichment capacity following the U.S. withdrawal from a deal designed to curb Tehran's nuclear program, Reuters reported, citing the country's nuclear agency chief.

The U.S. reimposed sanctions on Iran in May after pulling out of the accord, but Britain, France and Germany have been working to save the pact.

Tehran said it would remain in the agreement if its international trade were protected and its oil sales were guaranteed. But the country also said it would resume its 20% uranium enrichment, which is prohibited by the deal, Reuters said.

Supreme Leader Ayatollah Ali Khamenei reportedly said June 4 that he had approved preparations for greater enrichment capacity in case the deal could not be saved.

Ali Akbar Salehi, director of Iran's Atomic Energy Organization, said the move represented a quicker pace in the program's activities but did not run afoul of the nuclear deal. "If we were progressing normally, it would have taken six or seven years, but this will now be ready in the coming weeks and months," Salehi said.