Matson Navigation Co., citing a renewed rise in fuel costs, is increasing its fuel surcharge for its Hawaii-mainland service by 3.5 percentage points to 20 percent, effective June 21.

The state's largest ocean shipper also warned that if prices don't decline soon, it “;will need to make further upward adjustments.”;

Matson's increase follows a similar increase announced Monday by rival Horizon Lines Inc., which also is raising its surcharge the same amount from 16.5 percent. Horizon's surcharge will go into effect June 7.

In addition, Matson increased its surcharge by 3.5 percentage points to 21.5 percent, effective June 21, for its Guam/CNMI and Micronesia service. That follows Horizon's similar increase to 21.5 percent, effective June 7, for its Guam/ CNMI trade.

Both shippers had lowered their fuel surcharge six consecutive times in 2008—from 42.25 percent to 15 percent—until announcing a month ago they would increase their surcharge by 1.5 percentage points to 16.5 percent effective tomorrow.

“;Fuel prices escalated dramatically in the past month,”; said Dave Hoppes, senior vice president, ocean services, for Matson.

Pasha Hawaii, which transports vehicles from Honolulu to San Diego, is currently at 12.5 percent but said it “;very likely will be increasing”; its surcharge.