Yes, President Trump of the United States.
Trump stating he wants to make a trade deal
Trump has previously said in an interview with Piers Morgan (before the first extension):
So we are going to make a deal with the UK, that will be great. As you know, somewhat restricted. Because of Brexit you have a two year restriction. And when that restriction is up we're going to be your great trading partner. It's a tough restriction to have. You know for a couple of years, you have very strong lack of being able to do things.
Why a trade deal implies leaving the EU customs union
While Trump didn't mention no-deal specifically here, it's implied that the UK would be able to make trade deals which it is not the case when the UK takes on the EU's common external tariff. From the Institute of Government:
Accepting the EU’s common external tariff would also constrain the UK’s ability to strike new trade deals and require the UK to comply with substantial numbers of EU products regulations.
Evidence that President Trump knows (negotiating) a deal with the EU may hinder the UK's ability to negotiate its own FTAs
From Politico's Trump backs no-deal Brexit:
Trump also criticized the deal negotiated with the EU, particularly the post-Brexit transition period during which the U.K. would not be able to strike its own trade deals.
“One of the things that was, I think, very bad is to have this two-year moratorium on trade. That is terrible. That is a tremendous penalty," he said. “We have the potential to be an incredible trade partner with the U.K. We’re doing relatively little compared to what we could be doing with U.K. ... I think much bigger than European Union.”
A direct endorsement of walking away when "they don’t get what they want"
From Politico's Trump backs no-deal Brexit:
"If they don’t get what they want, I would walk away,” Trump told Britain's Sunday Times ahead of his state visit to the U.K., which begins on Monday. “Yes, I would walk away. If you don’t get the deal you want, if you don’t get a fair deal, then you walk away.”
Based on statements by former National Security Advisor Bolton
It has been pointed out that Bolton has left his function in the Trump administration. The way in which Bolton left is disputed, but it's clear that
it was due to differences in foreign policy views. Nevertheless, I am keeping this statement in as there has been no specific rebuke by the administation on this policy statement and Bolton's leaving wasn't directly after the statement was made.
According to Politico's US would ‘enthusiastically’ back no-deal Brexit, Trump envoy says:
America would "enthusiastically" support a no-deal Brexit, U.S. National Security Adviser John Bolton said on Monday during a visit to London.
“If that’s the decision of the British government, we will support it enthusiastically, and that’s what I’m trying to convey," Bolton told reporters on the first day of his two-day visit to the British capital, according to the Guardian. "We’re with you, we’re with you."
He said the U.S. would consider striking sector-specific deals ahead of a full-scale trade pact.
“The ultimate end result is a comprehensive trade agreement covering all trading goods and services,” Bolton said. “But to get to that you could do it sector by sector, and you can do it in a modular fashion. In other words, you can carve out some areas where it might be possible to reach a bilateral agreement very quickly, very straightforwardly."
Bolton also took aim at Brussels, saying: “The fashion in the European Union is when the people vote the wrong way from the way the elites want to go, is to make the peasants vote again and again until they get it right. There was a vote — everyone knew what the issues were. It is hard to imagine that anyone in this country did not know what was at stake. The result is the way it was. That’s democracy.”