Government eases oil import rules as it seeks to cut costs.

The Indian government has for the first time allowed state refiners to buy 35 percent of oil imports in tankers arranged by the seller, a document reviewed by Reuters showed, enabling them to swiftly tap cheaper cargoes.

The move will help refiners in Iran's second-biggest oil market to boost purchases from alternative sources as US President Donald Trump prepares to halt Iranian oil sales through a new set of sanctions from 4 November.

The measure is part of a series of attempts by the world's third-biggest oil importer and consumer to cut its surging oil import bill in the face of rising oil prices and a weaker Indian rupee.

India had previously allowed state-refiners to buy only 15.48 percent of their estimated 118.15 million tonnes of oil imports in the current fiscal year to 31 March on a Cost, Insurance and Freight (CIF) basis, meaning the seller arranges the vessel and insurance. The rest was largely procured on a Free on Board (FOB) basis to help Indian shipping lines and insurers.

More than doubling the percentage of CIF cargoes the refiners can buy gives them much greater flexibility to take advantage of more speculative or distressed sellers who need to sell their oil quickly.

This also indicates that Indian refiners will be in a position to purchase more US oil, which is mostly available on a CIF basis, helping to compensate for the loss of Iranian oil supplies. US crude is currently trading at a discount of about USD 10 a barrel to the Brent global benchmark price.

"Basically that (the new higher limit) has increased flexibility (for us) to look at opportunities that are available around the world and buy most economic cargoes," said one source at an Indian refinery who asked not to be named.

"It was difficult for us to take advantage of the situation when traders or companies are going around with material in the ships," this source said.

India's shipping ministry told the country's oil ministry about the move in a letter dated 19 September.

"Advance NOC (no objection certificate) is now granted to oil marketing companies to further import crude up to 23.07 million tonnes (balance 19.52 percent)," it said.