The UK is "first in line" for a trade deal with the US, President Trump's national security adviser has said.
John Bolton said the US supported a no-deal Brexit and added that Washington would propose an accelerated series of trade deals.
Mr Bolton claimed deals could be done on a "sector-by-sector" basis, with an agreement on manufacturing made first.
However, critics warned the UK would have to give in to some US demands in return for any trade agreement.
His comments came after meeting Prime Minister Boris Johnson at No 10.
According to Mr Bolton, a bilateral agreement or "series of agreements" could be carved out "very quickly, very straight-forwardly".
While saying that "both President Trump and I were leavers before there were leavers", he added that a trade deal for financial services and agriculture would not be the first to be agreed.
Mr Bolton said "doing it in pieces" is not unprecedented and the US understood the importance and urgency of "doing as much as we can agree on as rapidly as possible because of the impending 31 October exit date".
He argued that there would be enthusiastic bipartisan support in Congress for speedy ratification at each stage.
However, Sam Lowe, a trade expert at the Centre for European Reform said he was sceptical about whether Congress would support a "sector-by-sector" approach and the US had previously rejected an offer from the EU to negotiate on industrial goods before reaching an agreement on agriculture.
"The reason the US said no is because its aggressive ask when it negotiates with new partners is agriculture - that's what it cares about," he said.
Following his meeting with Mr Johnson on Monday, Mr Bolton said: "To be clear, in the Trump administration, Britain's constantly at the front of the trade queue, or line as we say.
"We want to move very quickly. We wish we could have moved further along in this with the prior government."
When asked whether his proposed plan would follow World Trade Organisation rules, he said "our trade negotiators seem to think it is".
Mr Bolton also criticised the European Union and accused them of treating voters like "peasants".
"The fashion in the European Union when the people vote the wrong way from the way that the elites want to go is to make the peasants vote again and again until they get it right," he said.
He made it clear that the US government "fully understands" that Brexit is the UK's first priority, and said issues like Iran, China, and the involvement of the Chinese telecoms firm Huawei in building the UK's 5G mobile infrastructure could be put off until after the UK leaves the EU.
"We just ask that, as issues come up, we resolve them individually and we reserve the time to have a larger conversation on some of these important issues at a moment that is really right for the new government. We just felt we owe them that," he said.
Mr Bolton also referenced Mr Johnson's willingness to participate in Operation Sentinel, which aims to beef up the military presence in the Gulf in the face of tensions between the West and Iran, saying he was "pleased" as this "reflects a change from the prior government".
'America first'
Former Labour foreign secretary Jack Straw described Mr Bolton as "dangerously bellicose", as well as opposed to
the Iran nuclear deal and international organisations like the United Nations.
In return for a trade deal, Mr Straw suggested the UK would have to agree to some US demands, for example allowing imports of US chlorine-washed chicken.
"This is a highly transactional administration… you don't get something for nothing," he told BBC Radio 4's Today programme.
Lewis Lukens, a former deputy chief of mission at the US Embassy in London and former acting US ambassador, said Mr Bolton was aligned to President Trump's "America first agenda" and would be making "strong demands" on the UK to back the US position on issues like Huawei, China and Iran.
For example, he said Mr Bolton would want a "clear indication" from the UK it would leave the Iran nuclear deal, which President Trump withdrew the US from in May 2018.
Mr Johnson is expected to have his first face-to-face meeting as prime minister with Mr Trump later this month at the G7 summit in France.