Traders have resumed offers of Russian crude cargoes to Indian refiners at narrower discounts after a delay triggered by recently imposed U.S. sanctions that have pushed up trading costs, Indian refining sources said on Friday.

Follow Bloomberg India on WhatsApp for exclusive content and analysis on what billionaires, businesses and markets are doing. Sign up  here .Russia is sending cargoes of sanctioned oil to India on tankers that have been blacklisted by the US Treasury — setting up an acid test of Moscow's ability to get around aggressive measures imposed by Washington earlier this month.

Russia has suffered a major economic setback, after China and India halted their purchases of Kremlin oil. Oil and gas revenues are vital sources of revenue, accounting for between a third and half of Russia 's federal budget over the last decade. In particular, these revenues play a key role in helping Putin to finance his war in Ukraine.

The United States has clarified to India that tankers loaded with Russian oil have to discharge by Feb. 27 under the latest sanctions targeting Moscow's oil revenue, India's oil secretary Pankaj Jain told reporters at an event.

Russia has continued to send cargoes of crude oil to India on tankers that have been sanctioned by the US, Bloomberg reported on Tuesday. This situation presents a crucial test of Moscow’s ability to circumvent the stringent sanctions implemented by Washington earlier this month.