HONG KONG : Oil prices fell on Monday as investors braced for details of a US plan to isolate the Iranian economy that President Donald Trump billed as the "most crushing" financial operation ever against Tehran.

Asian stocks were mostly down in early trading, with South Korea's tech-rich Kospi falling 1.4 percent after Samsung Electronics said it spent a massive $80 billion to buy back its own shares following weeks of turbulent trading.

The chip giant's shares, along with those of rival SK hynix, peaked in June on optimism for the artificial intelligence boom, but have since fallen amid investor jitters and a broader tech rout.

In an important week for artificial intelligence, investors are also looking towards an earnings report from Nvidia, the world's most valuable company and a bellwether for the sector.

The recurring question for the US chip maker is whether the AI boom will continue to accelerate as the technology takes over more corners of the broader economy.

"The spending machine is still running, but the bill is getting heavier," said Stephen Innes of SPI Asset Management.

"Nvidia must now show that the most expensive investment boom in modern market history can still pay its bills."

Chinese tech giant Alibaba is also keeping focus on the sector this week after announcing on Sunday that it plans to issue $10.2 billion in new shares in Hong Kong to fund its global AI ambitions.

The firm, known for its open-source "Qwen" AI models, has been ploughing tens of billions of dollars into artificial intelligence, with its shareholders eager to see how it will monetise the huge investments.

Tokyo, Shanghai, Taipei and Wellington were down on Monday. Sydney, Jakarta and Bangkok posted gains, while Manila and Kuala Lumpur were flat.

Eyes are also on US Treasury boss Scott Bessent, who he would give more details in a news conference on Monday on a fresh push to pile economic pressure on Iran.

The United States warned allies and China on Thursday to join Trump's new campaign, which comes as the unpopular war in the Middle East drags toward the six-month mark.

Vice President JD Vance admitted the plan was a "delicate dance" because Iran will "try to apply economic pressure to us".

Asked whether the United States would pressure China, Bessent told CNBC that "many conversations are best to have in private", but called on Beijing "to get with the programme".

Both main crude contracts were down 2.3 percent, with the Brent benchmark sitting at $92 a barrel.

Traders will also be watching this week's annual gathering of central bankers, economists and finance chiefs in Jackson Hole in the United States, hoping for some clarification on US monetary policy.

The meeting comes after the Treasury bought its own bonds last week in an effort to push down borrowing costs after the 30-year yield surged to levels last seen in 2007, just before the global financial crisis.

Yields have risen on inflation fears and as the United States reported that its federal debt had topped $40 trillion.