A United States spy agency on Sunday apologised for a sarcastic tweet aimed at China over its treatment of American reporters who had travelled with President Barack Obama to cover the G20 meeting.

"Classy as always China," the Defense Intelligence Agency tweeted on Saturday from its @DefenseIntel account.

"Earlier today, a tweet regarding a news article was mistakenly posted from this account & does not represent the views of DIA. We apologise," the Pentagon-housed spy agency tweeted on Sunday.

The initial tweet, which has since been deleted, included a link to a New York Times report about a dust-up over security protocols at the tarmac when Obama landed in China, and later, shouting matches between Chinese officials and Secret Service agents at the West Lake State House, where Obama met Chinese President Xi Jinping, CNN added.

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