WASHINGTON - US President Donald Trump desperately sought Friday to quell a growing storm triggered by his reported description of African nations, Haiti and El Salvador as "shithole" countries, in a slur denounced as "racist" by the United Nations.

Trump tweeted a convoluted denial early Friday but Democratic Senator Dick Durbin pushed back, saying the president repeatedly used the term "shithole" during a Thursday White House meeting on immigration reform.

"The language used by me at the DACA meeting was tough, but this was not the language used," Trump tweeted early Friday, apparently referring to the remarks quoted by the Washington Post and The New York Times. The Post, which cited people briefed on the meeting, quoted Trump as asking why the United States attracted immigrants from "shithole countries" such as African nations, Haiti or El Salvador, rather than - for instance - wealthy and overwhelmingly white Norway.

The New York Times reported the same comment, citing unnamed people with direct knowledge of the meeting. When a Democratic senator raised protections for Haitian immigrants, the Post said Trump responded: "Why do we need more Haitians?" adding: "Take them out." In a second morning tweet, Trump specifically denied he ever said "anything derogatory" about the people of Haiti. "Made up by Dems. I have a wonderful relationship with Haitians!" he posted.

But the government of Haiti - which Friday was marking eight years since a devastating earthquake killed at least 200,000 people in the country - declared itself "outraged and shocked."

Trump's reported comments drew similar protests from the 55-nation African Union, which called them "hurtful" and "clearly" racist, while the southern African state of Botswana hauled in the US ambassador to complain.

And they spurred a harsh reaction from the UN, with rights office spokesman Rupert Colville calling them "shocking and shameful."

"Sorry, but there is no other word one can use but 'racist'," he told reporters in Geneva.

"You cannot dismiss entire countries and continents as 'shitholes' whose entire populations, who are not white, are therefore not welcome", he added.

The White House meeting was held to discuss a proposed bipartisan deal that would limit immigrants from bringing family members into the country, and restrict the green card visa lottery in exchange for shielding hundreds of thousands of young immigrants from deportation. After making the "shithole" comment, Trump suggested the United States should instead welcome immigrants from places like Norway, whose prime minister he met on Wednesday.

"The positive comment on Norway makes the underlying sentiment very clear," Colville said, warning that Trump's comments should not merely be brushed aside as "vulgar language."

"It's about opening the door wider to humanity's worst side, about validating and encouraging racism and xenophobia that will potentially disrupt and destroy the lives of many people," he warned.

Trump cancels London trip

The British government blamed the threat of mass protests for President Donald Trump's decision Friday to cancel a visit to London to open the new US embassy, and warned that criticism of the White House risked harming US-UK relations.

Trump said he was abandoning next month's trip because he did not like the location and cost of the new embassy building.

But Foreign Secretary Boris Johnson suggested the decision was prompted by the opposition to Trump in Britain, and warned such critics "seem determined to put this crucial relationship at risk".

Prime Minister Theresa May offered Trump a state visit to Britain one year ago, when she became the first foreign leader to visit the White House after his inauguration.

But the date has yet to be set in the face of deep hostility to the president in Britain, prompting speculation it could be turned into a lower profile trip focused around the opening of the new embassy.

Trump tweeted overnight that he would not attend the ceremony, initially scheduled for next month.

"I am not a big fan of the Obama administration having sold perhaps the best located and finest embassy in London for 'peanuts', only to build a new one in an off location for 1.2 billion dollars," he wrote.

"Bad deal. Wanted me to cut ribbon - NO!"

His decision not to come was welcomed by critics outraged by the US travel ban on Muslim-majority countries, and more recently, Trump's decision to re-tweet anti-Muslim videos posted by a British far-right organisation.

"Many Londoners have made it clear that Donald Trump is not welcome here while he is pursuing such a divisive agenda. It seems he's finally got that message," tweeted Mayor of London Sadiq Khan.

The mayor, a member of the main opposition Labour party, said there would have been "mass peaceful protests", and that it had been a "mistake" to invite him.

There is likely some relief in the British government at Trump's decision, which would have caused at the very least a major policing operation.

But Johnson accused Khan and Labour leader Jeremy Corbyn of damaging US-UK relations with their vocal criticism.

"The US is the biggest single investor in the UK - yet Khan & Corbyn seem determined to put this crucial relationship at risk," he tweeted.

"We will not allow US-UK relations to be endangered by some puffed up pompous popinjay in City Hall."

A spokesman for May's Downing Street office said the invitation for the state visit "has been extended and accepted. No date has been confirmed".

"The US is one of our oldest and most valued allies and our strong and deep partnership will endure," he said.

Relations between May and Trump became strained in November after he re-tweeted anti-Muslim videos posted by a British far-right group.

May condemned it, and Trump hit back that she should focus on terrorism in Britain, which suffered five attacks last year.

In an article in London's Evening Standard newspaper on Friday, US ambassador Woody Johnson said Washington was "re-investing in the special relationship".

"Our new embassy reflects not just America's special history with the UK but the special future ahead of us as we advance the prosperity and security of both our nations," he wrote.

He conceded that the former building in upmarket Mayfair, central London, was a "perfect location" but noted it was viewed as too vulnerable following the September 11, 2001, attacks.