The statement came as trade talks between China and the United States were under way in Beijing, the first round of face-to-face discussions since both sides agreed to a 90-day truce in a trade war that has roiled worldwide markets.
Asian markets rose on increasing optimism that the two sides would be able to hammer out a deal ahead of a March deadline and avert further import tariff hikes.
He and Chinese President Xi Jinping agreed December 1 to postpone more tariff hikes on each other's goods for 90 days while they negotiate.
But a USA government official told AFP on condition of anonymity that "the trade talks have continued today (Wednesday)", without providing more information.
US President Donald Trump and Chinese President Xi Jinping in December agreed to put on hold a spiraling trade dispute of tit-for-tat import tariffs on hundreds of billions worth of goods.
Increased purchases by China of United States soybeans, oil, liquefied natural gas and financial services are viewed as easier to achieve than major changes to China's industrial policies aimed at transferring USA technology to Chinese firms.
The talks went ahead despite tensions over the arrest of a Chinese tech executive in Canada on USA charges she misled multinational banks about her company's business dealings in Iran.
"We have made stern complaints with the U.S.", Lu said.
The two delegations were led by U.S. deputy trade representative Jeffrey Gerrish and China's vice-minister of commerce Wang Shouwen.
United States companies also want action on Chinese policies they complain improperly favor local companies.
"If it's a good outcome, it doesn't just benefit the United States and China, but it is also good news for the world economy", said foreign ministry spokesman Lu Kang.
Chinese officials have suggested Beijing might alter its industrial plans but reject pressure to abandon what they consider a path to prosperity and global influence.
The negotiations appeared to have been making progress on areas such as China stepping up purchases of American exports and giving U.S. companies greater access to its market in order to build confidence between the two sides after months of bitter confrontation.
"There is further upside to come in prices, as we see more evidence coming through that members of OPEC+ are complying with their new production cut", said Warren Patterson, senior commodities strategist at ING Bank NV.
They've also promised to allow more foreign access to its auto, finance and other industries.
Chinese growth fell to a post-global crisis low of 6.5 per cent in the quarter ending in September.
The European Union filed its own challenge in the World Trade Organization in June against Chinese rules that the 28-nation trade bloc said hamper the ability of foreign companies to protect and profit from their own technology.
Officials have given scant details on concessions that China might be willing to make to meet US demands, some of which would require structural reforms unpalatable for Chinese leaders.
On Monday, Chinese importers made another large purchase of U.S. soybeans, their third in the past month.
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