Aug. 4 (Bloomberg) -- Supertanker owners are leaving more ships at anchor after rising fuel costs and the biggest weekly slump in hire rates for at least a decade made it less attractive to deliver cargoes.

The number of very large crude carriers, or VLCCs, at anchor climbed to 91 today from 82 on Aug. 2, according to AISLive ship- tracking data compiled by Bloomberg. The overall average speed of the global fleet fell 1.7 percent to 9.65 knots.

The benchmark hire rate, for cargoes to Japan from Saudi Arabia, plunged 46 percent last week to 123.13 Worldscale points, the fastest one-week drop since at least March 1998, according to data from the London-based Baltic Exchange. That represents earnings of about $59,461 a day after fuel costs.

Frontline Ltd., the world's largest owner of the vessels, and other ``major owners'' slowed the fleet by 20 percent toward the end of last year, curbing vessel supply by 10 percent, according to a May 2 regulatory filing from the company.

The possibility of another go-slow is ``soon again emerging'' because of rising fuel costs, Jens Martin Jensen, chief executive officer of the shipper's management unit, said in an e-mailed note July 10.

To contact the reporter on this story: Alaric Nightingale in London at Anightingal1@bloomberg.net

Last Updated: August 4, 2008 03:57 EDT