A deadly bomb trap discovered in Ardoyne on Tuesday is being viewed as a deliberate attempt by dissidents to stir up tensions in the lead up to the Twelfth.
The alert came as the seven-member Parades Commission was locked in last minute meetings before it made the controversial ruling on tomorrow's north Belfast feeder parade.
Its decision to allow a march in the morning but to stop the return leg has prompted an angry unionist reaction with renewed calls for the body to be scrapped.
As the fall-out over the decision continues, police have given few details about the bomb other than to say it was a bid to injure or kill officers.
But this newspaper understands the device was found inside a house and could have been triggered by anyone entering the property.
The alert began after reports of shots being fired in the area.
And it was during a follow-up search that the bomb was spotted inside a vacant but not derelict house.
"It could have been anybody opening that door," a PSNI source commented.
"It puts something else into the mix when we need to respond."
Several times in recent months dissidents have lured police into traps – with this latest incident being described by north Belfast SDLP MLA Alban Maginness "as a deliberate attempt to be provocative" leading up to the Twelfth.
Mr Maginness was involved in the weekend dialogue involving the local Orange lodges, residents, loyalist and republican leaders and politicians – talks that failed to reach agreement on tomorrow's march and meant a decision was left to the Parades Commission.
The seven members met over 10 hours on Tuesday – a decision on north Belfast taken on what one source described as "sufficient consensus".
Since the end of June, the Commission has been working on its Twelfth determinations with north Belfast "the last thing" to be decided.
Chief Constable Matt Baggott is appealing for calm and hoping for the best – but the decision to bring in extra support is also a clear indication of preparation and planning for all scenarios.