Published Tuesday, 13 October 2009
The Communication Workers Union says its members could walk out a week on Thursday.
Members voted in favour of industrial action in a row over jobs, pay and services last week.
The CWU warns it will press ahead with action if bosses don't accept their offer.
Assistant general secretary Dave Ward told Sky News everyone wants to avoid walkouts not just Royal Mail.
"If they are sincere about avoiding a dispute if they truly want to keep their customers satisfied then they will pick that offer up," he said.
"We want an agreement not a strike."