Brexit secretary David Davis has said the upcoming negotiations over the UK's exit from the European Union could be the most difficult diplomatic endeavour ever undertaken.
Speaking in front of a House of Lords committee, Davis said: "This is likely to be the most complicated negotiation in modern times, maybe the most complicated negotiation of all time."
He also said that the government will only declare elements of its negotiating strategy for leaving the European Union when it decides to trigger Article 50.
"At that point, we will have some clear negotiating guidelines. Before Article 50 is triggered will be a rather frustrating time as we won't be saying much," Davis said. "After, I expect it to be a more open process."
Read more: The Davis plan for Brexit
The Prime Minister has previously ruled out providing a "running commentary" on the UK's strategy for leaving the EU.
Davis, who was appointed to the head of the new department for exiting the EU by Prime Minister May, also fuelled the idea that Article 50 would be invoked early next year, despite calls from European officials to accelerate the process. He committed to establishing a clear negotiating strategy before the government would formally tell the EU it will be leaving the bloc.
"It's going to take some months to analyse many of the industrial and commercial effects. It's going to take some months to do the analysis on our negotiating partners, and some time on the legalities of the exercise."
The veteran Tory MP, who stood against David Cameron for leader of the party in 2005, also raised the possibility the government would not achieve everything it wants from Brexit.
"This is a negotiation," he said. "Where we go in at the beginning will not necessarily be where we end up. We're not going to preempt the negotiation." Davis also said the UK would need to be "nimble, fast and responsive" in order to wrap-up the negotiations within the two-year timeframe outlined under Article 50.
On the European Commission's chief negotiator, Michel Barnier, Davis downplayed the idea of personal animosity between the pair, but added: "He's a tough arguer, and a classically French negotiator".