Fresh talks this week to resolve a First Aberdeen driver strike have broken down without agreement.
Members of Unite at First Aberdeen are taking part in a week-long stoppage over proposed changes to their contracts.
A series of one-day strikes have already taken place. Aberdeen retailers have reported up to a 50% fall in customer numbers during the strikes.
Management at First met with representatives of Unite on Tuesday but could not reach agreement.
Andrew Jarvis of First Bus said he hoped the two sides were closing in on an agreement.
Unite says a meeting of drivers is planned for Thursday to discuss further possible action.