** Shares of some U.S. drugmakers fall premarket after U.S. President Donald Trump reiterated plans for a "major" tariff on all pharmaceutical imports as his "reciprocal" tariffs took effect

** Trump had also threatened the duties on Friday, after his first set of "reciprocal" tariffs announced last week exempted pharma products

** Shares of Gilead Sciences GILD.O down 2.6%, Eli Lilly LLY.N down 1.5%, Biogen BIIB.O down 1.1% and Pfizer PFE.N down 2.8%

** Amgen AMGN.O shares fall 2.3%, Merck MRK.N down 2%, AbbVie ABBV.N down 2.5%

** The U.S. president has said that the tariffs will incentivize drug companies to move their operations to the U.S.

** Brokerage BMO Capital Markets says the tariffs on pharmaceuticals will "likely do little to shift manufacturing back to the US" as the country already has robust biomanufacturing and fill-and-finish onshore

** Up to last close, LLY down 5.9%, MRK down 20.6%, BIIB down 25.4%, AMGN up 7.5% and GILD up 11.7% YTD

(Reporting by Christy Santhosh)

((Christy.Santhosh@thomsonreuters.com))