"They are just a trade bully", he told reporters in Geneva.
Others say the latest data shows how hard it will be for the U.S. to win the trade war, arguing that Americans want to buy Chinese-made products.
The US trade deficit with China hit a record high in June, according to a Reuters analysis, despite President TrumpDonald John TrumpGiuliani: Trump interview with Mueller "further away" ACLU calls for Trump officials to hand over info on immigrant children Kushner to join Pompeo for meetings with Mexican leaders MORE's efforts to alter the trade relationship between the world's two largest economies.
China's trade surplus widened sharply amid escalating trade tensions with the USA, which is preparing to impose fresh tariffs on a further $200 billion in Chinese goods.
Donald Trump had recently upped the ante by threatening higher tariffs on a colossal $200 billion of Chinese imports. That leaves about $80 billion for penalty tariffs after Beijing's previous increases either imposed or threatened on a total of $50 billion of USA goods are counted.
After a strong start to the year, growth in China's exports has moderated recently, and is expected to face more pressure from the initial round of U.S. tariffs.
"We expect the trade numbers for July to disappoint since that's when the first round of U.S. tariffs took effect", China analyst at Nordea Bank in Singapore Amy Zhuang told the BBC.
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As of Tuesday afternoon, more than 50 people were still listed as unaccounted for, the newspaper said . The scale of the disaster means the process of returning to normal life will be slow, officials said.
"Looking ahead, export growth will cool in the coming months as United States tariffs start to bite alongside a broader softening in global demand", Julian Evans-Pritchard, the senior China economist at Capital Economics in Singapore, said.
China imported American goods worth $13.6 billion in June while exporting $42.6 billion to the United States.
Mnuchin also said that the renegotiation of the North American Free Trade Agreement was a big priority for the administration now that Mexico's recent presidential election had passed.
In yuan terms, China's exports grew 3.1% in June and imports rose 6.0%.
In a sign Beijing is seeking alternative supplies of the commodities as it hit USA imports with extra tariffs, China had dropped import tariffs on a range of animal feed ingredients from several Asian countries.
Growth in imports for June showed a moderate slowdown from May, official data showed on Friday.
"We expect slowing export growth to put downward pressure on the current account and RMB (yuan), and believe China is likely to be willing to make concessions in future rounds of trade negotiations with the U.S.", Nomura analysts said in a note to clients.