Why Iran may find it difficult to clear its oil inventories even after sanctions relief

Iran is likely to face challenges in clearing its oil inventories even after restrictions on its energy imports are lifted, as its biggest customer tweaks its energy strategy while oil from other suppliers floods the market, according to analysts.

China, the world's top crude importer, has not been particularly enthusiastic about purchasing Iranian oil, despite traditionally being the country's main buyer. "In fact, the Chinese do not show any enthusiasm to buy much oil from anybody," Fereidun Fesharaki, chairman emeritus at FGE NexantECA, said on CNBC's "Squawk Box Asia."

China's crude imports have dwindled since the Iran war started in late February, depressing oil demand. In May, they plunged 29% from a year earlier to 7.82 million barrels per day, the lowest level since February 2018, according to Wind Information.

Chinese imports of crude from Iran more than halved in June to about 654,000 barrels a day compared with the prior month, Bloomberg reported.

The Middle East conflict has "sharpened China's strategic focus and injected renewed momentum into its green transition efforts," according to a report by Stockholm-based Institute for Security and Development Policy.

Chinese Premier Li Qiang has reiterated the need to boost non-fossil energy expansion and to build a new energy system, while encouraging innovation and quicker reforms, the research organization said.

Meanwhile, oil supply is also expected to increase after oil cartel OPEC+ agreed to add 188,000 barrels a day to their output target for August.

"The increase is part of the group's plan to finish reversing output curbs made a few years ago, and means they've added 940,000 barrels a day to quotas since the war began," according to a United Overseas Bank report.

"The supply surge is real," Tiago Lacerda, market analyst at brokerage Axi, said in an email to CNBC. He added that there was a sharp buildup at sea as Iran has shipped more than 40 million barrels since the U.S. lifted its naval blockade, while Russian exports have also surged to record levels.

The possibility of disruptions to oil flows via the Strait of Hormuz, however, might not entirely be discounted, which could complicate energy supply calculus.

Iran has been very clear that the current "free" passage in the Strait of Hormuz is only available for 60 days, after which they will start to impose tiered tolls, Fesharaki said, adding that "if you are my friend, you pay less. If you are not my friend, you pay more. If I don't like you, maybe I won't even let you take your oil through."

— CNBC's Anniek Bao contributed to the story.