A proposal for an immediate ban on travel from Britain to Northern Ireland has been defeated in a vote by the Stormont Executive.
Sinn Féin proposed the ban to combat the potential spread of a new, more contagious variant of Covid-19 during a remote meeting on Sunday.
The proposal was supported by the SDLP but opposed by DUP and UUP and Alliance Party.
After the proposal was defeated, ministers agreed, without a formal vote, to support recommendation by Health Minister Robin Swann to issue guidance against non-essential travel between Northern Ireland and Great Britain and Northern Ireland and the Irish Republic.
The Stormont Executive met last night to discuss the proposed travel ban after Mr Swann had sought guidance about the issue from Northern Ireland Attorney General.
Mr Swann said Stormont ministers were taking a "balanced and precautionary" approach but the new strain was a cause of serious concern.
He told a Stormont Assembly committee: "Act on the assumption that it is already present."
Mr Swann criticised the Irish Government's decision on imposing the travel bans without giving the Northern Ireland Executive prior knowledge.
Mr Swann said he is concerned about the residents of the Republic of Ireland using Belfast or Derry airports as a point of entry to the island.
He said: "I think it was unfortunate the Irish Government made the decision they did without any interaction or heads up to ourselves that that's what they were going to do.
"We've been very clear that if we want to act together and co-ordinate a response, it's better that we actually talk together before making decisions like that because it allows us to express or just concerns but also how we could possibly look towards common approaches rather than just one moving before the other."
Speaking to RTÉ's News at One earlier, First Minister Arlene Foster said that the six-week lockdown in Northern Ireland may be extended by an additional two weeks to keep ahead of the new variant of the virus.
She said "we must assume" the mutation is already present in Northern Ireland.
Ms Foster said there is a need to "double down on public health measures" to limit further spread and appealed to people to observe an upcoming curfew and other restrictions.
She said three positive cases with unusual sequencing have been sent to Public Health England for analysis but health experts have advised that it is likely the new strain has reached Northern Ireland.
The DUP leader said that people in Northern Ireland should now only gather together on Christmas Day, unless they are working in public or essential services that day, in which cases they can meet on Stephen's Day.
A further seven coronavirus deaths have been recorded in Northern Ireland and an additional 555 cases have been diagnosed.
The total number of confirmed cases of Covid-19 now stands at 62,497, with a death toll of 1,203.
Meanwhile, Stormont's Education Minister Peter Weir said he would introduce remote learning for secondary schools in Northern Ireland from 25 January.
Post-primary students in non-exam years will not return to the classroom from that date until February mid-term. He said schools must also be given the time to prepare for any change.
Mr Weir said he wanted to implement a package of measures in early January. He said consideration has already begun to extending the use of face coverings within post primary schools and how compliance on face coverings and safety measures can be increased on school transport.
Earlier, Mr Swann said he did not believe that a return to school as normal in January was a sustainable position.
"My view on this matter is informed by advice from the chief medical officer and chief scientific adviser."
Additional reporting Vincent Kearney