Leaders of the Communication Workers' Union and management agreed to meet next week in an attempt to avert what would be the first national walkout for eight years.
Richard Dykes, managing director of the Royal Mail, said last night that fresh proposals would meet concerns that the present offer left out more than 30 per cent of workers.
Alan Johnson, joint general secretary of the CWU, warned that staff would not simply be bought off. Key demands for greater efficiency would also have to be withdrawn.
On the first day of the CWU's annual conference in Blackpool, Mr Johnson said that all options for action would be explored including an indefinite national strike affecting deliveries to all 24 million addresses. Under employment legislation action will have to start by 28 June.
In a 74 per cent turnout, approximately 68 per cent voted for action to secure a reduction in the working week from six days to five. The union is also seeking enhanced job security, higher pay and assurances over the future of the second delivery. Growing distrust of management - which has led to 18 months of wildcat walkouts - has been fuelled by a series of proposals postal workers believe are aimed at achieving higher productivity without reward.
The CWU leader said the union wanted quick answers. "My members will take this action with great reluctance but they are the end of their tether. We want a five day week before the millennium."
A Royal Mail spokesman said more money would be put on the table so that no postal workers would lose out. "There is a very strong will at the Royal Mail to reach agreement. A strike is in no one's interest."