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Japan is the UK's 11th largest export market with the value of trade between the two countries reaching £29 billion (€32 billion) in 2018.
Failure to strike an agreement would mean a rupture in UK-EU relations, bringing trade friction, weaker security ties, and an end to many other mutual arrangements.
"The jungles of Brazil are at a breaking point," said Professor Britaldo Soares-Filho, co-author of the study.
The UK and the EU need to strike a deal on trade and future relations this year.
Our political editor Darren McCaffrey looks at the outcome of the G7.
Canberra and Brussels began talks in May 2018 and both sides of the negotiating table have clear demands.
The president says the tariffs will take effect June 10 and will stay until "illegal migrants" stop coming into the country from Mexico.