WASHINGTON (Reuters) - Bayer AG has pledged to boost its investments in the United States amid its deal to buy U.S. seeds giant Monsanto, investing $8 billion in research and development and adding American jobs, U.S. President-elect Donald Trump's spokesman said on Tuesday.

The German drugs and pesticides maker pledged to maintain its more than 9,000 U.S. jobs and add 3,000 new U.S. high-tech positions, Sean Spicer told reporters in a conference call following Trump's meeting with the chief executives of both companies last week.

(Reporting by Susan Heavey and Doina Chiacu; Editing by Chizu Nomiyama)