HANOI, Jan 26 (Reuters) - Fifteen U.S. semiconductors firms have expressed interest in investing $8 billion in Vietnam, a senior U.S. official said on Friday.

That investment is conditional on development of a renewables regime in Vietnam, Jose Fernandez, undersecretary for economic growth, energy and the environment at the State Department, told a press briefing in Hanoi. (Reporting by Francesco Guarascio; Editing by Martin Petty)