WASHINGTON (Reuters) - U.S. President Donald Trump said on Tuesday he will veto the National Defense Authorization Act unless the bill includes a measure eliminating a federal law protecting internet companies, known as Section 230. “If the very dangerous & unfair Section 230 is not completely terminated as part of the National Defense Authorization Act (NDAA), I will be forced to unequivocally VETO the Bill when sent to the very beautiful Resolute desk,” Trump tweeted late on Tuesday. Section 230 of the Communications Decency Act protects internet companies from liability over content posted by users and has been under attack from Trump and Republican lawmakers, who have accused tech companies of stifling conservative voices. The sweeping $740 billion NDAA sets policy for the Department of Defense. It has passed for 59 straight years, one of the few major pieces of legislation seen as a “must-pass” because it governs everything from pay raises for the troops to how many aircraft should be purchased or how best to compete with rivals like Russia and China. Earlier this year, the Democrat-led House and Republican-controlled Senate passed versions of the bill. It is in conference, where lawmakers come up with a compromise final version. Reporting by Eric Beech,Nandita Bose, David Shepardson and Mike Stone; Editing by Sandra Maler and Christian Schmollinger Our Standards: The Thomson Reuters Trust Principles.