The war in Iran has forced Japan’s biggest snack maker to replace its colourful packaging with black and white.

A global shortage of petroleum-based inks has left Calbee unable to get colours for 14 of its brands, including Potato Chips and Frugra Granola, according to reports.

The company announced it would temporarily switch from its bright designs to monochrome packaging later this month.

This was in response to “supply instability affecting certain raw materials amid ongoing tensions in the Middle East”, Calbee said.

Coloured inks are made from byproducts of the oil refining process, such as naphtha.

But the closure of the Strait of Hormuz has sent oil prices soaring around the globe and caused shortages of these byproducts.

Calbee’s snack packets lose their colour. Photo: Supplied

Japan reportedly relies on the Middle East for about 95 per cent of its crude oil imports and 60 per cent of its naphtha.

In March, analysts from Citigroup estimated Japan only about 20 days of naphtha, according to Yahoo Finance.

Brent crude oil futures extended gains on Tuesday, climbing to almost $US108 ($149) a barrel, as a US-Iran deadlock left the Strait of Hormuz largely closed.

Before the war began on ‌February 28, the narrow waterway ‌carried a fifth of the world’s ⁠oil and liquefied natural gas shipments, and has since become a central pressure point in the conflict.

Hopes for a peace deal on Iran ‌have dwindled after US President Donald Trump said the ceasefire with Iran was “on life support”.

Tehran rejected the US proposal to end the conflict and stuck to a list of demands Trump has described as “garbage”.

Iran has called for ‌an end to the war on all fronts, including Lebanon, where US ally Israel is fighting Iran-backed Hezbollah militants. Tehran also emphasised its sovereignty over the Strait of Hormuz, demanded compensation for war damage, and an end to the US naval blockade, ‌among other conditions.

Trump said Iran’s response threatened the status of the ceasefire announced on April 7.

“I would call it the weakest right now, after reading that piece of garbage they sent us. I didn’t even finish reading it,” Trump, who has repeatedly threatened to end the ceasefire, said.

The US had proposed an end to fighting before starting talks on more contentious issues, including Iran’s nuclear program. In Washington, the Pentagon put the cost of the war at $US29 billion ($40 billion) so far, an increase of $US4 billion ($5.5 billion) from an estimate provided late last month.

Trump is expected to arrive in Beijing on Wednesday, where Iran will be among the topics discussed with Chinese President Xi Jinping.

Traffic through the Strait of Hormuz is at a trickle compared with before the war. Shipping data on Kpler and LSEG showed that three ​tankers ​laden with crude exited the waterway last week, with trackers switched off to avoid an Iranian attack.

-with AAP