Nippon Steel Corp. and JFE Holdings Inc. will raise wholesale prices for steel sheets by 10 percent as early as June, according to three metal traders familiar with price talks.

The boost follows a 25 percent increase to about ¥100,000 in April and is needed to cover an unexpected tripling in annual coking coal prices, said the traders, who declined to be identified because price talks are confidential.

Nippon Steel, the world's second-largest steelmaker, reportedly is seeking increases of as much as ¥30,000 a ton, or 38 percent.