Almost 1.4 million Dubliners face the threat of new Covid-19 restrictions if skyrocketing case numbers are not brought under control.
There is increasing concern in Government about the situation in Dublin with 182 new cases announced yesterday.
The Cabinet discussed the rise in cases in Dublin and Limerick when they met to sign off on allowing all pubs reopen on September 21.
After the meeting, senior Government figures warned it was highly unlikely pubs in Dublin would reopen in two weeks if the rate of new cases continued to rise at its current trajectory.
Tánaiste Leo Varadkar also told his parliamentary party he was "very worried" about the number of new cases in Dublin.
And two Cabinet ministers said they would not be surprised if some form of restrictions were introduced in the capital soon.
Meanwhile, an advertising campaign will be launched in Dublin to urge people to be more cautious and limit their social interactions.
The outbreaks in the capital are in mostly family or home settings rather than pubs, restaurants or other places where people gather.
However, if cases continue to rise in Dublin, new restrictions will have to be considered, a Cabinet minister said.
"The problem is that you can't impose the same restrictions you imposed on Kildare and Offaly on Dublin," the minister said.
"The debate is around how do you close down Dublin if you have to."
Another minister said the outbreaks were focused in the west of the city and the concern is that a lot of the cases are community transmission which means they cannot be easily traced.
"The majority of the cases are in the Dublin West and Dublin South West constituencies," they added.
Another senior Government source said: "Everyone in Dublin should be mindful that Covid figures are way up - and we all need to make a conscious effort to limit our social contact in controlled settings."
It came as the Archbishop of Dublin Diarmuid Martin urged caution among priests and churchgoers.
The bishop said social distancing in "some cases has become loose" after Mass.
"I have seen some examples in our Dublin churches and indeed some parishes have published photos on parish websites that indicate poor practice," Dr Martin said.
"I would ask all parishes to examine carefully how they can foster staggered exiting from churches and prevent gatherings at church entrance," he added. "In addition, I would remind parishes that the norms which permit gatherings of up to 50 people or "pods" of 50 people in Church buildings applies to religious services alone. For any other gatherings such as meetings or concerts, the limit is six people," he added.
The archbishop also noted that international evidence showed that masks rather than visors were better for protecting the public against the virus.
The Nphet advice was given to the Government last Thursday and included new guidelines for pubs to follow when they reopen.
This includes a ban on any live music or dancing. Public health experts also recommended that TV volume must be turned down low to ensure people are not forced to speak over it.
International research has shown the virus spreads more quickly among people who are raising their voices - such as those attending sporting events or in other crowded situations.
Nphet also said some pubs may need to introduce extra toilets facilities to allow for social distancing.
Pubs may also have to limit the number of customers they can have at any time depending on the size of the premises. Nphet added nightclubs and discos should remain closed for the foreseeable future.