Bombardier is Northern Ireland's largest manufacturing employer

More than 1,000 jobs are under threat at the company's Belfast operation following a decision by workers to reject a proposed four-year agreement over pay.

Wednesday's talks were described as "constructive," both by Bombardier Aerospace and by a union source.

Both sides have agreed to meet again on Sunday in an effort to break the deadlock.

The company said more substantive negotiations would be held next week, if some issues could be cleared up.

The unions said in a statement that further discussions were scheduled to take place on Tuesday and Wednesday next week.

The company had already announced 580 redundancies in response to what it called "very challenging market conditions".

Peter Williamson from the manufacturing, science and finance union Amicus, who is leading the union's delegation in the talks, said workers wanted recognition for their achievements.

Union leader Peter Williamson: Workforce are angry

"I know the workforce are extremely annoyed, they are extremely angry," Mr Williamson said.

"It has certainly never been my experience as a trade union official to witness the resentment and the anger that is current in this workforce at this stage."

Mr Williamson said employees had met deadlines, schedules and targets.

"They are turning some profits in the company, considerable profits in the Bombardier group.

"They see all of that taking place and there is this reward that people expect in those circumstances."

Bombardier in Canada has already made it clear that it needs to reduce the workforce in Northern Ireland in order to improve competitiveness.

It said it was essential that the company was "in the best position possible to retain contracts with its customers who are demanding very competitive, long-term price commitments".

The aerospace industry has been badly affected in recent years by events including 11 September, the consequent fear of terrorism, the downturn in the global economy, competition from low-cost carriers and the recent Sars outbreak.

Many airlines are in financial difficulties and have cancelled some aircraft orders and putting others on hold.