By Gerry Shih and Noel Randewich

BEIJING/SAN FRANCISCO, Sept 25 (Reuters) - Intel Corp is close to announcing an investment in Chinese-government affiliated mobile chipmakers Spreadtrum Communications and RDA Microelectronics, its latest move to catch up in a smartphone chip industry led by Qualcomm Inc , according to two sources with knowledge of the plan.

It was unclear how much Intel is paying or what portion of the companies the U.S. chipmaker is buying. The acquisition could be made through Tsinghua Unigroup, a government-affiliated private equity firm controlled by Tsinghua University in Beijing, one of the sources said. Tsinghua Unigroup owns Spreadtrum and RDA.

Struggling to gain traction in the smartphone and tablet market, Intel has recently sought to partner with mobile chipmakers in the hope they could help it regain the market dominance it enjoyed when personal computers reigned.

An Intel spokesman declined to comment.

(Reporting by Noel Randewich and Gerry Shih, editing by Peter Henderson)