LONDON, March 27 (Reuters) - The Qatar Investment Authority, the Gulf Arab state's acquisitive sovereign wealth fund, is setting up an office in San Francisco to manage its growing portfolio in the United States, its CEO said in London on Monday.

"Soon we will be opening an office in the Silicon Valley in San Francisco," Sheikh Abdullah bin Mohammed bin Saud al-Thani told reporters at an investment conference.

The fund is one of the most active sovereign investors in the world, snapping up stakes in everything from real estate to luxury goods.

Much of its activity has traditionally been in Europe but the fund has said it is looking to diversify into Asia and the United States.

Qatar said in 2015 it would spend $35 billion in the United States over the next five years after opening an office in New York.

The QIA has about $334 billion of assets according to industry tracker Sovereign Wealth Center.

(Reporting by Tom Finn and Kylie Maclellan, editing by Stephen Addion) ((Tom.Finn@thomsonreuters.com;))