Adm. Harry Harris, the U.S. Pacific military chief known for his combative views on Beijing's South China Sea expansion, is expected to step down next year, U.S. officials said on Friday, leaving President Donald Trump to fill a key post closely watched by China.

Harris, who was appointed by President Barack Obama, could end his term as head of Pacific Command (PACOM) after three years in May, two sources with knowledge of the potential change told Reuters. Most PACOM commanders serve three years but there is no official term limit.

A U.S. official said that while the timing could be right, the process of replacing Harris — starting with a nomination to the Senate Armed Services Committee — had not yet begun.