** U.S.-based solar companies rise premarket as trade officials in the United States on Monday finalized steep tariffs on most solar cells from Southeast Asia
** This is part of a year-old case where U.S. firms had accused Chinese companies of flooding the market with unfairly cheap goods and endangering their U.S. investments
** Tariffs targets major Chinese solar firms such as Jinko Solar 688223.SS and Trina Solar 688599.SS
** Cambodian products to face duties of more than 3,500%
** Finalization of tariffs hinges on a June vote by the International Trade Commission, assessing whether the industry suffered material harm from cheap imports
** First Solar FSLR.O up 5.8%, SolarEdge Technologies SEDG.O 2.6%, Sunrun RUN.O 1.5% and Enphase Energy ENPH.O 2.5%
(Reporting by Pooja Menon in Bengaluru)
((Pooja.Menon@thomsonreuters.com))