The request was made during a meeting between US and Japanese officials in Tokyo this week, according to the report by Bloomberg.
No decision has been made yet, though, and talks will continue.
This means that Washington is taking a harder stance on Iran than it did in 2012. Six years ago, before the 2015 nuclear deal between Tehran and world powers, the US demanded that its allies should reduce oil purchases from sanctioned Iran, rather than stop them completely.
Japan is Asia’s fourth-largest buyer of Iranian crude, which accounts for 5.3 percent of its oil consumption, or 172,000 barrels per day.
Refiners in Japan earlier said they could substitute Iranian oil with crude from other Middle Eastern countries, even though their plants are particularly compatible with crude from Iran.
Some analysts see the demand as a negotiating tactic before trade talks begin between the US and Japan.
“It could be that the US is initially demanding a big thing before offering Japan a way to go around it in negotiations,” Satoru Yoshida, a commodity analyst at Rakuten Securities said.
“Even if the US is asking Japan to completely stop Iranian crude imports, which is a very high hurdle, it may lower its demand later.”