The nation's largest truckload carrier will start charging its customers more if Union Pacific Railroad doesn't recover from its service problems soon.

The rate warning from Schneider National came as UP was struggling to unscramble service problems that have jammed up portions of the country's largest rail network amid indications that other railroads were seeing capacity shortages.

The problems at UP that have built up since the beginning of the year have sent shippers looking for alternatives and one key customer, UPS, was hoping to get its intermodal traffic back on the UP network this week after pushing trailers meant for express trains onto the highways.

Schneider National gives UP 3,000 53-foot domestic containers a year for line-haul between ports, distribution centers and retail outlets. Most of the truckload giant's intermodal business moves with UP rival Burlington Northern Santa Fe Railway. Still, the Green Bay, Wis.-based $3 billion transportation and logistics company says its intermodal pricing will rise as the strain on UP's network grows.