Police are anticipating roads to ports in the north being blockaded during potential Brexit-related protests.
PSNI Chief Constable Simon Byrne has appealed for more officers to help his overstretched force.
He said he has not detected a massive change in sentiment and has no intelligence to suggest unrest is likely.
However, officers are trained and ready to respond and more body armour is being organised in case extra police from other parts of the UK have to be drafted in for support, he added.
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"We can only anticipate some planning assumptions, whether it is some blocking of roads, access to the ports is one scenario, but we have no specific intelligence at all at the moment that is what is planned," he said.
Police prepare for possible Brexit protests by loyalists at N Ireland ports. pic.twitter.com/I0O1cRD4oP
— Mark Simpson (@BBCMarkSimpson) December 19, 2019
"You can see that peaceful protest - which is where we want to start - can take a variety of forms and we need to facilitate that but also minimise disruption to people that want to go about their day-to-day business if that happens."
Under British prime minister Boris Johnson's Brexit plan, customs tariffs could be imposed on goods travelling between Britain and the north instead of on the border to protect the EU's single market.
Unionists are adamantly opposed to what they term a border in the Irish Sea.
Mr Byrne said he was not reacting to specific intelligence of a threat from loyalists in Belfast or the port areas.
"We are clearly using tried and tested practice to make sure we have a good dialogue with communities right across Northern Ireland.
"We build up intelligence where we need to and we have officers who are trained and equipped and ready to respond to protest.
"We are not seeing massive change in sentiment at the minute so I don't want to alarm people, but you would also expect me and my colleagues to be prepared for any change over the next few weeks and months."
Northern Ireland has major ports in Larne in Co Antrim and Belfast, serving freight and passenger traffic from Scotland and north-west England.
The future of the border and the threat posed by dissident republicans had been the primary focus for police planners earlier in the Brexit negotiations process.
Mr Byrne is bidding for extra officers to augment 300 already granted for Brexit duties.
He said: "It is about turning the lens from the border to the ports, so we will be asking for people."
Mutual aid provisions allow other forces around the UK to augment PSNI numbers if necessary and Mr Byrne said they are looking at the supply of body armour.
He said: "We need more officers on the front line."
The DUP is opposed to Mr Johnson's Brexit plan, accusing him of facilitating an economic united Ireland.
Policymakers are juggling the need to prevent a hard border on the currently frictionless frontier between the north and Republic with unionist concerns about preserving the integrity of the UK.
Mr Byrne said planning was well advanced.
Addressing a meeting of the Policing Board in Belfast, he said: "Given where we are, I am as confident as I can be."
