Oil prices have risen after plans for a second round of peace talks between the US and Iran stalled again.
Brent crude, the global benchmark for oil prices, rose over 3% to over $109 (£80) a barrel on Monday before falling back slightly.
US President Donald Trump said on Saturday that Washington had cancelled plans to send a team to Pakistan for negotiations with their Iranian counterparts.
Global energy supplies have been under intense pressure since the start of the Iran war as the crucial Strait of Hormuz waterway has been effectively closed by the conflict.
Iranian Foreign Minister Seyed Abbas Araghchi said on Sunday that "important discussions on bilateral matters and regional developments" were ongoing with Oman, its neighbour along the strait.
He posted on social media: "Our focus included ways to ensure safe transit that is to benefit all dear neighbors and the world. Our neighbors are our priority."
Araghchi arrived in St Petersburg on Monday "with the aim of meeting and holding talks with Russian President Vladimir Putin", Iranian state-run news agency Irna reported.
Around a fifth of the world's crude oil and liquified natural gas (LNG) usually passes through the Strait of Hormuz.
Brent crude has risen by more than 10% since Trump announced last week that he would extend a ceasefire with Tehran to give its leadership a chance to present a "unified proposal".
Sophie Huynh, a portfolio manager and strategist at BNP Paribas, said the ongoing closure of the strait could affect the price of everything from "bin bags to medicine".
"I think we're underestimating the extent of which products could be affected by the oil shortage," she told the BBC's Today programme. "We're not consuming crude, we're consuming products."
If the strait remains closed for more than a few weeks, the effects will be "really far reaching in terms of supply chain", she said.
Oil traders appear to be less reactive to the latest headlines and are waiting for "credible" evidence of the conflict easing, said economics lecturer Goh Jing Rong from the Singapore Management University.
"I think traders want concrete evidence rather than just a fragile and reversible ceasefire agreement," Goh said.
Trump wrote in a Truth Social post on Saturday that there was "too much time wasted on travelling" and "too much work" in sending US representatives to Islamabad.
The president added that "there is tremendous infighting and confusion" within Tehran's leadership.
"Nobody knows who is in charge, including them," he said. "Also, we have all the cards; they have none! If they want to talk, all they have to do is call!!!"
In the UK, representatives from the Bank of England will attend the government's Middle East Response Committee meeting on Tuesday, which will include discussions on the effects of the conflict on people's living costs.
Addressing the impact of the war on the UK, Prime Minister Sir Keir Starmer said the economic consequences "could still be with us for some time".
"What Iran shows is that once again events happening miles away from Britain have the capacity to hurt our living standards, our future and our security," he said in a speech on Monday.
The surge in oil prices since the start of the conflict has already led to rising fuel prices at the pump, and there are concerns over how much UK energy bills could rise later this year if the conflict continues.
On Monday, the S&P 500 index of the largest firms listed in the US closed flat as traders assessed the situation in the Middle East.
London's FTSE 100 index closed 0.6% down, France's Cac 40 ended the day 0.2% lower, and Germany's Dax finished flat.
Stock markets in Asia closed higher, with some major stock markets hitting record highs despite having fallen sharply at the start of the conflict.
Japan's Nikkei 225 index ended 1.38% ahead, adding to a rise of nearly 14% in the past month.
The Kospi in South Korea has jumped by more than 20% in the past month, finishing up by 2.15% on Monday.
Japanese and South Korean stocks were initially hit hard as their economies are heavily reliant on energy supplies from the Gulf.
