US Defense Secretary Chuck Hagel arrived in Singapore on Friday for an Asia-Pacific security conference at which he is expected to press China on cyberattacks and reaffirm Washington's strategic shift to the region.

The Pentagon chief is expected to urge Beijing to agree to "rules of the road" to mitigate cyber threats after a US report found evidence of a broad Chinese spying campaign against top US defence contractors and government agencies.

"The United States knows where many of these incursions come from," Hagel told reporters on his plane as he travelled to the Shangri-La Dialogue, an annual international security conference in the city state.

"It's pretty hard to prove that they are directed by any specific enemy but we can tell where they come from and we've got to be honest about that."

His comments came after a Pentagon report found that Chinese hackers have gained access to secret designs for a slew of sophisticated US weapons programs, possibly jeopardising the US military's technological edge.

During his four-day stay in Singapore, Hagel is expected to meet many of his Asian counterparts although there will be no high-level talks with the Chinese.

However, Pentagon officials said he would have the opportunity to speak with Chinese military officials on the sidelines of the talks.

General Martin Dempsey, the Chairman of the Joint Chiefs of Staff, visited Beijing in April and Hagel has invited his Chinese counterpart Chang Wanquan to Washington in August, while President Barack Obama is set to meet with new Chinese leader Xi Jinping next week in California.

At last year's Shangri La Dialogue, then US defense secretary Leon Panetta announced that the majority of the US naval fleet would gradually be shifted to the Pacific region as part of the pivot towards Asia.

"The focus is really follow-through this year," a senior defence official who spoke on condition of anonymity said ahead of Hagel's visit, his first to Asia since taking over in February.

"Last year, we were sharing with the region the new strategic guidance. This year is really about showing that that strategic guidance, the rebalance, is under way," the official told reporters.

While in Singapore, Hagel is due to pay a visit to the USS Freedom, the first of the new Littoral Combat Ships that will be based out of the port. The ship deployments are touted as part of the US strategic focus on Asia.