Saudi Arabia has begun to explore extracting lithium from sea water
Speaking to reporters on Air Force One during his return to Washington from Cape Canaveral in Florida, Trump said the G7, which groups the world's most advanced economies, was a "very outdated group of countries" in its current format.
"I'm postponing it because I don't feel that as a G7 it properly represents what's going on in the world," Trump said.
It was unclear whether Trump's desire to invite the additional countries was a bid to permanently expand the G7. On several previous occasions, he suggested Russia be added, given what he called Moscow's global strategic importance.
Russia was expelled from what was then the G8 in 2014 when Trump's predecessor, Barack Obama, was US president, after Moscow annexed the Crimea region from Ukraine. Russia still holds the territory, and various G7 governments have rebuffed previous calls from Trump to readmit Moscow.
White House spokeswoman Alyssa Farah said Trump wants the countries to discuss China at the summit.
Trump has attacked Beijing over its handling of the coronavirus pandemic, which began in China, and on Friday he ordered his administration to begin the process of ending special US treatment for Hong Kong in retaliation for China's decision to impose a new security law on the former British colony.
The decision to postpone the G7 summit is a retreat for Trump, who had sought to host the group of major industrialized countries in Washington as a demonstration that the United States was returning to normal after the coronavirus epidemic, which has killed more than 103,000 Americans to date.
Trump had cancelled an in-person G7 meeting scheduled for March as the virus spread, but had recently sought to revive it.
French President Emmanuel Macron backed the idea of an in-person meeting, according to the White House, but Canadian Prime Minister Justin Trudeau declined to endorse it, saying there were too many health-related questions. This week, German Chancellor Angela Merkel said she could not attend.
South Korea is aware of Trump's invitation and will discuss the matter with the United States, a government official in Seoul told Reuters on Sunday.
The G7 groups the United States, Britain, France, Japan, Germany, Italy and Canada, and the European Union also attends.
Saudi Arabia has begun to explore extracting lithium from sea water
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