Siemens CEO Joe Kaeser attends the company's annual news conference in Munich, Germany, November 9, 2017. REUTERS/Michael Dalder - RC12652D94E0

FRANKFURT (Reuters) - Siemens will test the appetite of sovereign wealth funds ahead of the planned listing of its healthcare unit Healthineers next year, its chief executive told a German weekly, possibly to secure anchor investors for the flotation.

The listing of a minority of the unit, which makes X-ray and MRI machines, is set to take place in the first half of 2018 and is expected to value Healthineers as a whole at around 40 billion euros ($48 billion).

Siemens is expected to sell 15-25 percent of Healthineers, sources have said, implying stock worth 6-10 billion euros could be sold - Germany’s biggest share offering since Deutsche Telekom in 1996.

“Internal preparations are going well and we are still planning the listing in the first half of 2018, if markets play along,” Joe Kaeser told Frankfurt Allgemeine Sonntagszeitung in an interview published on Sunday.

“In any case, we are planning to test the interest of relevant anchor shareholders, including sovereign wealth funds.”

Asked whether this included Norway and China, home to the world’s largest and third-largest state funds, respectively, Kaeser said: “We will probably cover the range of the most important state funds, yes. The advantage would be that we would gain anchor investors. The disadvantage: the free float of shares is not as high.”

The move is designed to enable the unit to raise its own funds for takeovers and investments in the healthcare sector as well as crystallizing its standalone value, removing some of the “conglomerate discount” that weighs on Siemens’ valuation.

In 2016, utility RWE won BlackRock as an anchor investor in the initial public offering of its Innogy unit. RWE ended up selling a 23.2 percent stake in the networks, renewables and retail unit.