The Royal Mail has confirmed it has been notified of potential strike action.
Workers in Inverness and Oban told the Press and Journal it was likely strike action, if approved by union members, after ballots were returned on July 19.
Given that 14 days notice is needed for strike action is required, the earliest date would be August 2.
In a statement, Royal Mail said there were “no grounds” for industrial action.
Royal Mail received formal notice from the Communication Workers Union (CWU) today, saying the union intends to ballot its members for industrial action.
A Royal Mail spokeswoman said: “We believe there are no grounds for industrial action. We offered a deal worth up to 5.5% for CWU grade colleagues, the biggest increase we have offered for many years, which was rejected by the CWU.
“We have further talks on change with CWU this week.
‘We remain committed to a deal’
“We hope this will ultimately lead to an agreement on the changes required to ensure Royal Mail can grow and remain competitive in a fast-moving industry, securing jobs for the future and retaining our place as the industry leader on pay and terms and conditions.
“We value the work we do with CWU and remain committed to agreeing a deal for tomorrow, not just today.”
Not wanting to be named, workers in Inverness and Oban told the Press and Journal they were being asked to do an impossible task with diminishing numbers of staff – and industrial action was the only way they believed the matter could be resolved.
One said: “At the moment we are working flat out to cover our own routes and then the routes of staff members that are not being replaced.”
Another said: “It’s only in the early stages of planning so far, but I guarantee you it will be a vote of yes for striking.
“The managers know a strike is coming and it’s going put them in a big hole, because Royal Mail aren’t budging much so there is no progress with the union.”
CWU general secretary Dave Ward said: “Our members have been treated in a completely undignified manner by the people they make incredible profits for.
“Our members kept this country connected throughout our country’s greatest crisis since the Second World War, and many paid the ultimate sacrifice.
“Now, they are being told there’s nothing for them, and they have to accept having less while the mega profits of bosses come first.
“The state of affairs is unjust and unsustainable, and I have no doubt that our 115,000 members will stand strong against it and deliver a historic vote for action.”
Terry Pullinger CWU, deputy general secretary for postal workers, said: “Nobody wants to be in this situation, but our members are heroes.
“We will defend ourselves if provoked – and we are convinced we will receive our biggest ever ‘yes’ vote for action.”