US Defense Secretary Chuck Hagel on Saturday accused China of waging cyber espionage against the United States, stepping up pressure on Beijing over the issue ahead of a key summit between their leaders.

US Defense Secretary Chuck Hagel on Saturday accused China of waging cyber espionage against the United States, stepping up pressure on Beijing over the issue ahead of a key summit between their leaders.

Speaking at a Singapore security forum attended by senior Chinese military officials, the Pentagon chief pointedly blamed the Chinese government and armed forces for repeated intrusions into sensitive US information systems.

"The United States has expressed our concerns about the growing threat of cyber intrusions, some of which appear to be tied to the Chinese government and military," he told an annual conference known as the Shangri-La Dialogue.

Hagel pressed Beijing to adhere to "international norms of responsible behaviour in cyberspace", while acknowledging that the establishment of a joint cyber security working group was a positive step in fostering US-China dialogue on such issues.

The Singapore forum came ahead of the June 7-8 meeting between US President Barack Obama and his Chinese counterpart Xi Jinping in California, the two leaders' first meeting since Xi took office in March.

Hagel's remarks came just days after China's defense ministry dismissed a Pentagon report released in May accusing Chinese hackers of accessing US weapons designs.

The report was the most explicit statement yet from Washington that it believes China's cyber spying is focused on the US government and corporations.

Last year, Washington announced a major naval deployment to Asia, including the rotation of up to four Littoral Combat Ships -- newly developed vessels designed for coastal operations -- to Singapore, a staunch US supporter.