SINGAPORE, April 6 (Reuters) - Spot premiums for U.S. West Texas Intermediate crude have jumped to all-time highs as competition between Asian and European refiners for supply heats up to replace Middle Eastern oil flows disrupted by the Iran war, industry sources said.

Europe is typically the largest importer of U.S. crude, but competition has escalated with Asian buyers scouring for supply from the Americas to Africa and Europe to replace Middle Eastern oil that is unable to move through the Strait of Hormuz.

The jump in crude prices is driving up costs and widening losses for refiners on both continents, sources and analysts said, putting severe pressure on companies including state-owned firms that are required by governments to keep producing fuel for national security.

"Asian refiners, shut out of Middle Eastern supply, are bidding aggressively for every available Atlantic Basin barrel," said Paola Rodriguez-Masiu, chief oil analyst at Rystad Energy, in a note dated April 3.

'EVERY DAY THERE'S A NEW PRICE'

Offers for WTI Midland crude delivered to North Asia in July on very large crude carriers had premiums of $30 to $40 a barrel, depending on the benchmark used, traders said.

One trader pegged the premium at $34 a barrel to Dubai quotes while another put it at $30 a barrel above dated Brent. Two others said offers have gone closer to $40 a barrel above an August ICE Brent basis.

Those levels are up from premiums of close to $20 a barrel for deals concluded in late March and early April, when Japanese refiners including Taiyo Oil purchased WTI crude, traders said.

"Every day there's a new price," one of the traders said, adding that Asian refiners face severe losses from the premiums.

Another trader said refiners would be better off reducing crude runs and buying products - if anyone is offering.

Spot premiums jumped after the prompt monthly spread for WTI futures hit its widest backwardation on Thursday. Backwardation refers to when prompt prices are higher than those in future months.

Wider discounts on U.S. crude oil compared with global benchmark Brent have also spurred demand for tankers on the U.S. Gulf Coast, reducing vessel availability in the region and driving up freight rates.

In Europe, bids for WTI Midland delivered to the continent climbed to a record premium of close to $15 a barrel against dated Brent on Thursday. [CRU/E]

"At current physical differentials and freight rates, European refiners buying spot crude cannot make money running those barrels through their systems," Rodriguez-Masiu said.