Writing in an opinion piece for the Belfast Telegraph, she said there were three main reasons why the proposed backstop agreement with the EU should be supported.
She said: “This agreement ensures that there can never be a return to the borders of the past in the event that we have not entered into our future relationship by 2021.
“Although it is important to restate that both sides agree that we never want to use it, and will both be legally bound to use our best endeavours to reach agreement on the future in good time, I understand and share some of the concerns that have been expressed.
“I believe the following three points make this an acceptable insurance policy: first, there is the opportunity to extend the Implementation Period instead of entering the backstop; second, the Government will keep regulations consistent across the whole of the UK in order to minimise any checks or controls and ensure no divergence between Northern Ireland and Great Britain; and third, this is expressly temporary, with a mechanism by which it can be terminated.
“And of course, in this situation, Northern Ireland would benefit from frictionless access to both the EU and the rest of the UK markets.”
She said Northern Ireland was now in a “fantastic position” with guarantees on the country’s future as part of the United Kingdom and avoids the cliff-edge of a no deal for Northern Ireland.
She also addressed how Brexit will impact Northern Ireland’s policing, economy and the Irish border, which proved to be the most contentious issue in the Brexit negotiations.
Further defending her plans for Northern Ireland, she said: “The challenge of Brexit has always been to continue our deep trading links and security cooperation with the EU in our new relationship, whilst freeing us to take advantage of the opportunities, such as an independent trade policy.
“This deal strikes that balance, and puts Northern Ireland in a fantastic position for the future.
“Northern Ireland’s constitutional status as part of the United Kingdom is guaranteed, with the Belfast Agreement and the consent principle enshrined in this deal.”
The Prime Minister tried to persuade Northern Irish business owners by highlighting leaders who have already pledged support for her deal.
She said: “When it comes to the economy, as business leaders in Northern Ireland from the CBI, FSB, IoD and Chamber of Commerce have recognised, the Withdrawal Agreement will provide the clarity and certainty that business needs.
“It ensures they will have time to adjust to our new relationship, avoids a cliff edge, and therefore protects jobs and investment.”
On policing in Northern Ireland, the Prime Minister said security along the Irish border is one of the most important aspects of a future relationship with the EU.
She wrote: “The Chief Constable of the PSNI has demonstrated why there is nowhere where our policing and security cooperation with the EU is more important than in Northern Ireland.
“It is vital that we are able to share information and work together as we do now.
“I welcome the progress we have made on data exchange and extradition but we need to go further.
“This is one of the most crucial elements of our discussions with the EU this week.”