International Trade Secretary Liam Fox has cast doubt on whether Britain will obtain a "gold standard" trade deal with China after Brexit.
And he acknowledged that any new free trade agreements will only come into effect "some time away", following a transition period out of the EU expected to last until 2021.
Speaking during a three-day visit to China with Theresa May, Dr Fox gave his full support to the Prime Minister remaining in office "as long as she wants to lead my party".
And he said that Mrs May's internal critics would take a different view of her if they could see how she was being received by international leaders such as Premier Li Keqiang and President Xi Jinping.
Asked whether he believed Mrs May would be leader by the time of the next general election, Dr Fox told ITN: "I will give full support to the Prime Minister as long as she wants to lead my party.
"I think she is doing an excellent job and I do wish more of my colleagues could see the sort of leadership and commitment and positive agenda that's been projected for Britain here in China."
In a round of TV interviews in Beijing on the second day of the visit, Dr Fox said it was right for the UK to focus on trade links with Asian giants like China, telling the BBC: "By 2030 China will have 220 cities of more than a million people. The whole of Europe will have 35. Where should we be focusing our attention?"
But he suggested that deals with China after Brexit may not take the form of a full-scale free trade agreement.
"We are looking to see where we can get improvements, whether its done with a gold standard free trade agreement, whether it's done by a series of measures for market access and mutual recognition or equivalence - the whole range of tools in the box," he told Sky News.
Mrs May has already accepted that it will not be possible for new free trade agreements with countries outside the EU to take effect until after the end of what she terms the "implementation period" of around two years following Brexit day on March 29 2019.
And Dr Fox acknowledged: "We haven't got to Brexit yet, of course, and that may be some time away if we've got an implementation period.
"But what we're doing is to ensure that when we have economic freedoms we can take advantage of them.
"We've set up a trade and investment review with China to take a look at the options we have in terms of our trading relationship and agreements once we have left the EU. But in this short term that doesn't mean we can't increase our trade."
The Government expects £9 billion worth of trade and investment deals to be sealed during the Prime Minister's visit.
Dr Fox said these included £1 billion in financial services agreements, a £750 million deal by energy giant BP and an agreement by a Chinese e-commerce outlet to sell £2 billion of UK goods over the next two years.
"All of this adds up to a much-improved trading performance," he told the BBC. "And remember, the more we're able to sell abroad, the more revenues we generate, the more tax revenues we generate, and the more income there is for our public services."