The newly appointed U.S. Treasury secretary "pressed hard" in meetings with Chinese leaders over alleged Chinese cyber attacks aimed at stealing commercial secrets from American companies, according to U.S. officials.
Jack Lew raised the issue at a meeting on Wednesday with Li Keqiang, China's new premier, in the Pavilion of Purple Light in Beijing's central leadership compound, an official said.
"It has to be recognized, as the president indicated, this is a very serious threat to our economic interests," Mr Lew said after the meeting. "There was no mistaking how seriously we take this issue."
Mr. Lew's visit to Beijing, the first by a senior member of President Barack Obama's new cabinet, was timed to coincide with the formation of a fresh Chinese government, headed by Xi Jinping, who formally took over as state leader last week.
The meetings were the first in public for Mr. Xi and Mr. Li in their new roles and also Mr. Lew's opening meetings with foreign leaders since he was confirmed as Treasury secretary in February.
In his discussion with Mr. Li, Mr. Lew distinguished between cyber attacks suffered by many governments and hacking by state-sponsored Chinese entities aimed at stealing commercial secrets.
China has been accused by foreign governments, companies and cyber hacking experts of supporting large-scale efforts to extract trade and commercial secrets from global companies.
When confronted by such accusations, China has invariably denied any involvement in cyber hacking and insisted that it is itself a major victim of hacking attacks.
Congress in particular has become infuriated by what its members say is a wave of attacks, including from China, on U.S. interests, and support has been building for some kind of retaliation.
In Wednesday's discussion with Mr. Lew, Mr. Li acknowledged the Treasury secretary's remarks but did not respond at length, according to a US official.
The two sides also discussed China's exchange rate, a perennial topic in such talks for almost a decade that has slipped down the agenda following steady appreciation in the renminbi by more than 30 percent against the dollar in eight years.
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Mr. Lew said he had raised the issue in his meetings with leaders and stressed that the value of the renminbi should be "market-determined".
Earlier on Wednesday, in a meeting with a group of U.S. companies in China that included Boeing, Ford, General Electric, FedEx and JPMorgan Chase, Mr Lew was told that cyber security and protection of intellectual property and trade secrets were top priorities for them.
Mr. Lew also discussed North Korea and its recent nuclear test. "We made clear that the U.S. views the provocative actions of North Korea as very serious and we will continue to pursue methods available to change the policy perspective in Pyongyang," he said. "[China and the U.S.] share a common objective of a denuclearized Korean peninsula and we will continue to discuss it."