Patna: Soaring petrol and diesel prices have returned to haunt as state owned petroleum companies raised fuel prices for the fourth day in a row on Sunday and experts said the Donald Trump administration's Iran ultimatum was partly to blame.

On Sunday, petrol was at Rs 81.66 per litre while diesel was at Rs 72.57 per litre at the HP filling station on Bailey Road opposite Bihar Museum in Patna. Fuel prices vary marginally by location and filling station.

"We hoped for a major cut in fuel prices but our hopes went in wane," said Ashish Singh, medical representative with a pharmaceutical company. "Now there are statements coming out that petroleum products would be brought under GST (goods and services tax), but what its impact on prices will be is unclear to us.

"Petrol and diesel are essential commodities and the surge in prices impacts the people's lives substantially. Almost everything becomes costlier, including the cost of transportation. As the prices began to increase again we need to readjust our household budgets again," Ashish said.

Patna University student Vikas Kumar also felt the only hope of fuel price reduction was through the GST. "As lawmakers and officials are now talking about inclusion of petroleum products under GST, we support the idea if it will reduce the prices and provide relief to the common man," said Vikas.

Finance secretary Hasmukh Adhia on Friday said that the GST council would work to bring petroleum products under the indirect tax regime in a phased manner. However, experts are sceptical on and feel it is unlikely that GST would reduce petrol and diesel prices.

As of now, petrol, diesel, crude oil, natural gas and aviation turbine fuel are outside the purview of GST. The Centre levies Rs 19.48 excise duty per litre of petrol and Rs 15.33 per litre on diesel. The states also levy value added tax (VAT). The Bihar government imposes 26 per cent and 19 per cent VAT on petrol and diesel respectively.

"The recent northward movements in fuel prices in India perhaps caused by the uncertainty after Donald Trump administration had told countries trading with Iran to bring oil imports from Iran to zero by November 4 or face US sanctions," said Prabhat Kumar Sinha, president Bihar Petroleum Dealers' Association. "As the country in the Persian Gulf is the third largest oil supplier for India, the concerns over supply disruptions have pushed prices higher here."

N.K. Choudhary, former head of department of economics at Patna University, said the falling rupee was another factor.

"Besides the uncertainty over Iran and GST, the recent decline in the value of Indian rupee against the US dollar is leading to imports becoming costlier," he said. "When the value of the rupee declines importers including oil companies have to pay more, which increases their costs and puts additional pressure on fuel prices in the country."