Li, in his first news conference after being elected premier last week to succeed outgoing Wen Jiabao, said cyberattacks have become a worldwide problem and China itself is a major victim.
"China does not support but indeed opposes such attacks," Xinhua News Agency quoted Li as saying.
"We should not make groundless accusations against each other and spend more time doing practical things that will contribute to cyber security," the new No. 2 leader of China said.
Li, an economist and an advocate of economic reforms in his country, spoke of rapid growth in China-United States bilateral trade, from about $1 billion three decades ago to over $500 billion last year. He said more opportunities in trade and investment between the two countries would emerge in coming years.
"I don't believe conflicts between big powers are inevitable," Li said. "Shared interests often override their disputes.
"The Chinese government, as always, highly values the ties between the world's most powerful country and the biggest developing country. We're willing to construct, together with the Obama administration, a new type of relationship between big powers."