After weeks of easing fuel costs, average petrol prices in the United States have climbed back to $4 per gallon, driven by the recent flare-up in the Middle East and rising tensions between the US and Iran. According to motor club federation AAA, the national average price of regular gasoline stood at $4 per gallon on Monday, compared with $3.14 per gallon during the same period last year.The average masks significant differences across the country. Motorists in several states have already been paying more than $4 per gallon for some time, while prices remain lower elsewhere. The variation is driven by factors including local fuel supply and state tax rates.The latest increase follows a period of easing prices. The national average first moved above $4 per gallon at the end of March before dropping below that level in mid-June. Fuel prices continued to soften after the US and Iran reached an interim deal, which led to lower crude oil prices. At the time, President Donald Trump voiced frustration that petrol prices were not falling as quickly as oil prices.That trend has now reversed as crude prices have risen in recent days after the US and Iran launched more attacks, raising concerns that the two countries are moving closer to resuming an all-out war.The impact is not limited to the United States. People in countries around the world are also facing higher fuel costs as a result of the war.The rise in petrol prices could also have wider economic implications, with higher fuel and oil costs capable of pushing up the prices of groceries and other goods. Fuel affordability is also likely to remain an important issue for voters in the upcoming US midterm elections.Meanwhile, in the oil market, Brent crude, the global benchmark, climbed 3.2% to $90.95 a barrel, while US benchmark crude rose 2.8% to $84.04 a barrel.