Theresa May's Brexit plans will strengthen in the years after the UK has left the European Union, according to the Welsh secretary.
Alun Cairns told BBC Wales that the so-called Chequers plan contained the main elements needed for honouring the result of the referendum in 2016.
But he also insisted that Brexit was a "process, not an event" - a phrase coined to describe devolution in Wales.
Mrs May's proposals for leaving the EU were agreed by the UK cabinet in July.
It includes a "common rulebook" for all goods traded with the EU and a "facilitated customs arrangement" which aims to maintain frictionless trade in goods between the UK and the EU whilst allowing Britain to develop an independent trade policy with the rest of the world.
However, European Council President Donald Tusk said on Thursday the Chequers plan "will not work".
Speaking at the end of an EU summit in Salzburg, Austria, on Thursday he said the proposals risked undermining the single market.
Mr Cairns, MP for the Vale of Glamorgan, said the plans could be changed after the UK leaves the EU at the end of March next year:
"Brexit is a process, not an event - in the same way that devolution was described as a process, not an event," he said.
"We'll all remember the first form of devolution in Cardiff Bay was quite a weak form.
"Last year I took an Act through parliament which strengthened it to make it a full law-making Parliament in Cardiff Bay. That's been part of a process.
"I also see Brexit on the same basis, that we absolutely have to honour the outcome of the referendum. We must leave the European Union next year."
Mr Cairns denied that meant the prime minister's plans were a weak Brexit, insisting it was important to ensure "a smooth process to leave the European Union".
"But we will see the divergence of the economy between Europe and the UK take place over time, and that great goal of signing those international trade arrangements," he added.
The Chequers proposals led to two high-level resignations from the Cabinet - Foreign Secretary Boris Johnson and Brexit Secretary David Davies.
Many pro-Brexit Conservative MPs believe the idea of a common rule book and combined customs territory will erode British sovereignty and claim it was not what people voted for when they backed Leave in the 2016 referendum.
Mr Cairns criticised those he claimed were working to undermine the prime minister.
"How do they think they can move from one position to a very different one overnight when we can have an implementation period, we can have that divergence over time?"
Plaid Cymru Carmarthen East and Dinefwr MP Jonathan Edwards said the "irony of co-opting the 'devolution is a process not an event' phrase to describe Brexit must be lost on Alun Cairns".
"Not only do we face a sudden Brexit cliff edge thanks to the incompetence of his Westminster Government, he is responsible for working with Labour to push through legislation - under the cover of Brexit - that rolls back devolution."
Mr Edwards said Plaid would "oppose this economic and constitutional catastrophe the Welsh secretary wishes to inflict on our country".