By Agence France-Presse
President Donald Trump asked the US Trade Representative consider increasing the proposed tariffs to 25 percent from the announced 10 percent, US Trade Representative Robert Lighthizer said.
"We have been very clear about the specific changes China should undertake. Regrettably, instead of changing its harmful behavior, China has illegally retaliated against US workers, farmers, ranchers and businesses," Lighthizer said in a statement.
Officials however downplayed suggestions the move was intended to compensate for the recent decline in the value of the Chinese currency, which have threatened to take much of the sting out of Trump's tariffs by making the imports cheaper.
Washington and Beijing are locked in battle over American accusations that China's export economy benefits from unfair policies and subsidies while stealing American technological know-how.
Trump has threated to slap tariffs on virtually all of China's exports to the United States.
On July 10, Washington unveiled a list of another $200 billion in Chinese goods, from areas as varied as electrical machinery, leather goods and seafood, that would be hit with 10 percent import duties.
Increasing the rates to 25 percent could make them significantly more painful.
"We will give people a chance obviously to comment on the substantial effects of a 25 percent duty as oppose to a 10 percent duty," a senior administration official told reporters.
The comment period on the proposal, which includes public hearings on the tariffs due to take place later this month, would be extended into September, the officials said.
The US already imposed 25 percent tariffs on $34 billion in Chinese goods, with another $16 billion to be targeted in coming weeks.