Senior staff at St Paul's Cathedral are continuing to meet City of London Corporation (CLC) officials over the decision to close it - the first time since World War II.
Up to 300 protesters from Occupy London Stock Exchange have now been camped in the churchyard for a week and have refused to leave.
The dean has cited health and safety concerns for the closure decision.
One CLC member called on them to disband in a peaceful manner.
The cathedral would normally attract thousands of visitors on a Saturday but they will be turned away although some weddings and other services are expected to take place.
Sunday services have also been suspended.
The action by the cathedral authorities and the Dean, the Right Reverend Graeme Knowles, follows appeals to the group whose numbers have grown during the week in protest at what they call "corporate greed and inequality".
In a statement published on the cathedral's website, Dean Knowles said they were left with "no lawful alternative" but to close St Paul's.
The decision had been taken "with a heavy heart" but it was "simply not possible to fulfil our day to day obligations to worshippers, visitors and pilgrims in current circumstances".
"With so many stoves and fires and lots of different types of fuel around, there is a clear fire hazard," he said.
"Then there is the public health aspect, which speaks for itself."
'Not a stunt'
"The dangers relate not just to cathedral staff and visitors but are a potential hazard to those encamped," it added.
But the protesters claim they have tried to answer such concerns, reorganising their camp "in response to feedback from the fire brigade".
OccupyLSX said in a statement they had been working "to accommodate the cathedral's concerns in any way we can".
The protesters have however, decided to continue with the action following a meeting which is thought to have taken place on Friday.
One of the group, who gave her name as Lucy, said: "This protest is massive, it affects everybody, everyone's watching at home right now.
"It's not just about a few people who have got some tents in St Paul's, it's not a stunt, it's not a spectacle."
Stuart Fraser, policy and resources committee chairman on the CLC, said he was still hopeful "common sense will prevail" and that those camping around the cathedral "will recognise that they are damaging the integrity of their protest by their actions - and they decide to disband in a peaceful manner".