Theresa May's promise to make a Brexit work for the United Kingdom looks to be approaching yet another major hurdle in the form of Norway.

That is because the Nordic state's European affairs minister, Elizabeth Vik Aspaker, said her government could block the UK from trying to rejoin the single market, as it's not in Norway's interests.

Prime Minister May has said that she wants to secure a Brexit which will allow Britain to remain part of the EU's single market. Some Brexit supporters have suggested joining the European Free Trade Association (EFTA) — a small group of states which has access the single market despite not being EU members — would be the best way of doing this.

However, the UK's route into the EFTA will not be as straightforward as it perhaps first seemed. "It’s not certain that it would be a good idea to let a big country [the UK] into this organisation," Vik Aspaker told the Aftenposten newspaper. "It would shift the balance, which is not necessarily in Norway’s interests."

She also confirmed that the UK could only join the EFTA if the current members reached a unanimous agreement. The current members are Norway, Iceland, Liechtenstein, and Switzerland. In theory, Norway, or any other EFTA member, could exercise its veto and block UK from pursuing a key element of its Brexit project.

(The diplomat who oversaw Greenland's exit from the EU says a Brexit is an "enormous" challenge which will take "much longer" than three years.)

One of the major concerns for the Norwegian government, the Aftenposten report says, is that Norway would have to renegotiate a host of trade agreements if the UK were to join. This would be an incredibly long and complex process.

Norwegian Prime Minister, Erna Solberg, urged Brits to resist voting for a Brexit in the run-up to the June 23 referendum. "Do not leave the EU," she said. "You will hate it."

The challenge facing Theresa May and her ministers of withdrawing the country from the EU seems to be getting more complex and unrealistic with each day that passes. This reality was summed up perfectly by legal expert David Allan Green, who writing for the Evening Standard on Tuesday, said:

"Making something happen is not the same thing as merely wishing for it. It may be near-impossible for the UK to leave the EU, at least in the next few years. And just as the brutal fact that the British people voted to leave the EU cannot be ignored, the fact that leaving the EU may not be possible cannot be ignored either."

Green could not be closer to the truth. The challenge facing May and her government is huge. Last month, Business Insider noted how various EU diplomats had accused the UK of being "nowhere near" establishing what the terms of Brexit should be. You can read about this here.

Note: This article was amended so that European Economic Arena (EEA) was corrected to European Free Trade Association (EFTA).