US President Donald Trump has signed legislation that intensifies sanctions on Russia, particularly its oil and mining industries, and places new sanctions on North Korea and Iran. The law also gives Congress the power to veto the easing of sanctions on Russia by the president. Trump had little choice but to sign the bill as it was passed by overwhelming majorities in the Senate and the House. The sanctions on Moscow are in retaliation for Russia's aggression in Ukraine and alleged interference in the US presidential election. In a statement on Wednesday, Trump claimed the legislation was "seriously flawed" as "it encroaches on the executive branch’s authority to negotiate", but said he signed it "for the sake of national unity".