Britain has invited Australia, India and South Korea to the Group of Seven summit it will be hosting in 2021 as guest nations, the Prime Minister's Office said Tuesday.

Prime Minister Boris Johnson invited India to attend the summit in a letter sent to his Indian counterpart Narendra Modi prior to his visit next month to the South Asian country, the office said.

It said in a statement that Johnson wrote to Modi to invite India "as one of three guest nations alongside South Korea and Australia -- delivering the prime minister's ambition to work with a group of like-minded democracies to advance shared interests and tackle common challenges."

Other G-7 members are Canada, France, Germany, Italy, Japan and the United States, plus the European Union.

Earlier this year, U.S. President Donald Trump had called the current G-7 framework "very outdated" and expressed a desire to expand the group to include Australia, Brazil, India, Russia and South Korea.

Many G-7 countries remain reluctant to bring Russia back into the forum due to its failure to reverse course after annexing Crimea from Ukraine in 2014, over which Moscow was expelled from the former Group of Eight.

Japan has been nervous about moves toward expanding the forum as it enjoys the position of being the sole Asian representative under the current grouping of advanced countries.