US Trade Representative Robert Lighthizer said there was "no justification" for China's retaliation.

"As in the past, the United States is willing to engage in efforts that could lead to a resolution of our concerns about China's unfair trade practices and to China opening its market to US goods and services," he said.

"In the meantime, we will remain vigilant in defending the ability of our workers and businesses to compete on a fair and reciprocal basis."

'Increasingly worried'

Many companies in the US are opposed to the administration's use of tariffs against China, saying they risk hurting business and the economy without being likely to change behaviour.

On top of the $34bn worth of tariffs that came into effect on Friday, the White House has said it would consult on tariffs on another $16bn of products. President Trump has suggested these could come into effect later this month.

In total, the new import taxes President Trump is threatening to impose are almost equal to the value of China's entire goods exports to the US, worth more than $500bn last year.