Indefinite strike action by staff protesting against a private finance initiative project was due to start this week at one of London's largest trusts.
Unison called for 1,000 members to strike against University College London Hospitals trust's plans to start transferring support staff to private contracts shortly after its PFI contract is signed.
It wants UCLH to delay transfer until completion of the development in 2003.
Spokesman Phil Thompson said that members had been called on to join 'continuous strike action' for an initial period of two weeks.
He said that UCLH managers were 'not prepared to discuss the matter', adding: 'It is difficult to see any other way of resolving it.'
But the trust said it had held a number of meetings involving Unison and contractors and that negotiations were not suspended until the decision was taken to strike.
A trust spokesperson added: 'This is why we feel that industrial action is actually disadvantageous to the staff they purport to
The trust claims that just 2 per cent of staff joined in a one-week strike on the same issue last month.