Talks aimed at heading off fresh postal strikes were adjourned last night and will resume today.
Leaders of the Communication Workers Union met with Royal Mail bosses for seven hours at the headquarters of the TUC in London.
TUC general secretary Brendan Barber said neither side would be making any comment after yesterday's meeting.
Mr Barber said: "The Communication Workers Union and the Royal Mail have been meeting today at the TUC to discuss all the issues involved in the current dispute.
"We have had useful discussions today and the talks are being adjourned to allow further work to be done overnight on some of the issues involved.
"We will be reconvening again in the morning here at Congress House to continue the talks.
"In the meantime neither the CWU nor the Royal Mail will be making any further comment."
Dave Ward, deputy general secretary of the union, said as he arrived for the talks this morning that ministers could not continue "sitting on the sidelines".
Mr Ward said the dispute was "fundamentally" about jobs and workers' terms and conditions.
"The change that postal workers are facing is on a scale that's greater than any other UK industry at the present time and I think what we are going to do today is end that confusion about what this dispute is about," he said.
He said the issue of the Royal Mail's pension deficit - which totals about £10 billion - needed to be resolved urgently.
"There's no prospect of us building a successful future for the Royal Mail and for the workforce unless the Government actually deal with that issue," he said.
"That's why we keep saying the Government can't keep sitting on the sidelines."
He added: "We will deal with the issues around the industrial side of the Royal Mail but there are things that the Government have to deal with. Unless we fund a solution to the pensions deficit very quickly then this company has no prospect of building a successful future."
Royal Mail said the volume of delayed mail caused by last week's strikes by the CWU is expected to have fallen to five million items by the end of today.
The company said 30 million items had been delayed by two 24-hour walkouts on Thursday and Friday, but employees returned to work on Saturday and started tackling the backlog.
Royal Mail said it wanted to apologise again to customers for the disruption and delays caused by the strikes.
Up to 120,000 CWU members are set to stage three further 24-hour strikes from Thursday unless the deadlocked row is resolved at the TUC talks.Reuse content