The number of cases in England has soared in the last two weeks because of a variant of the coronavirus is up to 70 per cent more transmissible, according to scientists.
UK PM Boris Johnson told a Downing Street briefing that the "new variant of the virus" had altered the government's understanding of the coronavirus situation in the country.
"Because the science is clearly changing and has changed in the sense that our understanding of this new virus, its transmissibility, has been radically shifted just in the last 24 hours," Johnson said.
"We simply can't ignore that and that's why we're taking these extra steps today to protect the country."
People in tier 4 areas will be required to stay at home except for essential reasons such as work. Non-essential retail will close, as will indoor leisure and entertainment. Social mixing will be limited to meeting one other person in an outdoor space.
Trump has expressed numerous times that he is against imposing another nationwide lockdown in the US.
He has been criticised over his response to Covid-19, with more than 300,000 Americans dying from the pandemic and nearly 17.5 million infected.
