Washinton DC - Japan and India are struggling economically because they are "xenophobic," President Joe Biden told a campaign event, lumping the US foreign allies in with rivals China and Russia as countries rejecting immigrants.

"Why is China stalling so badly economically? Why is Japan in trouble? Why is Russia in trouble? And India? Because they're xenophobic. They don't want immigrants," Biden said on Wednesday, with a transcript not made public until Thursday.

The 81-year-old Democrat, who is seeking reelection against Republican rival Donald Trump in the November presidential vote, made the remarks at a campaign fundraising event in Washington marking the start of Asian American, Native Hawaiian, and Pacific Islanders Heritage Month.

Such events are neither filmed nor recorded, but a small number of journalists attend and provide a written account.

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"One of the reasons why our economy is growing is because of you and many others. Why? Because we welcome immigrants," the president said.

While China and Russia are considered US rivals, Biden's remarks on Japan and India came as a surprise.

Since taking office in 2021, Biden has made a point of strengthening ties with US allies in Asia, in particular with New Delhi and Tokyo.

He has hosted state dinners – a rare high-level diplomatic gesture – for both Indian Prime Minister Narendra Modi and Japanese Prime Minister Fumio Kishida.

The White House sought to downplay the president's remarks on Thursday.

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"The broader point the president was making, and I think people all around the world recognize this, is that the United States is a nation of immigrants, and it's in our DNA," National Security Council spokesman John Kirby told reporters.

"Our allies know very well how much the president respects them, values their friendship, values their contributions," he added.