WASHINGTON — The Trump administration readied new sanctions Tuesday on North Korea, a day after declaring it a state sponsor of terrorism in a move to put additional pressure on Pyongyang’s nuclear program. North Korea has joined Iran, Sudan and Syria on America’s terror blacklist, a largely symbolic step as the administration already has the authority to impose virtually any sanctions it wants on Kim Jong Un’s government over its nuclear weapons development. As part of its “maximum pressure” campaign, President Donald Trump said the Treasury Department would impose more sanctions on North Korea and “related persons” starting Tuesday, without hinting who or what would be targeted.