On Saturday, Yellen met Vice Premier He Lifeng, and bowed effusively on meeting the top Chinese official.

Beijing’s official Xinhua news agency said the meeting yielded an agreement to ‘strengthen communication and cooperation on addressing global challenges’. 

Yellen said Sunday told a press conference that her talks with top Chinese officials have helped put ties on ‘surer footing’. 

Former White House staffer Bradley Blakeman, who served during President George W. Bush’s administration, told the New York Post that Yellen’s kowtowing to the Chinese official was inappropriate.

‘Never, ever, ever – an American official does not bow,’ said Blakeman. ‘It looks like she’s been summoned to the principal’s office, and that’s exactly the optics the Chinese love.’

Blakeman added: ‘The way to treat an adversary is, you don’t go hat in hand. ‘But with this administration, time and time again, we embarrass ourselves and show weakness.

‘And it just shows the lack of effective leverage we have.’ Author Max Murray said: ‘She did not realize bowing as an American official was a breach of protocol.

‘They don’t reciprocate. He even backs away to give her more space to kowtow.’