Treasury Secretary Jack Lew will press China to take "serious steps" to investigate and stop cyber-attacks on U.S. companies and other entities and urge the administration of new Chinese President Xi Jinping to accelerate economic reforms, a senior official said on Friday.

Lew's visit to Beijing on Tuesday and Wednesday "comes at an important moment," the official said, speaking to reporters on condition of anonymity. "China is undergoing their once-in-a-decade leadership transition and, of course, their reform process is at a crossroads."

"It's important to deepen our relationship with China's new leadership team at this time," the official said

(Reporting by Doug Palmer; Editing by Vicki Allen)