WASHINGTON - US President Donald Trump on Friday said he wished people would "sit up at attention" for him like North Koreans do for their leader Kim Jong Un, a joke that sparked instant outrage on social media and cable news.It was the latest example of a Trump remark about strongmen leaders - delivered in a deadpan style - to fall flat and fuel perceptions among his critics that the president admires autocrats.Trump was asked during a Fox News Channel interview outside the West Wing if he would invite Kim to the White House. The two met earlier this week to begin to discuss Pyongyang's nuclear program, a summit marked by what Trump said was friendly chemistry between them.Trump indicated a White House visit by Kim was possible: "Hey he's the head of a country," Trump said."He speaks and his people sit up at attention. I want my people to do the same," Trump said, pointing to the West Wing.Kim is suspected of ordering the assassination of his half-brother in February and the execution of his uncle in 2013. UN investigations have also reported human rights violations, the use of political prison camps and the widespread use of starvation as a tool to enforce political loyalty.Trump was later asked by reporters what he meant by the remark. "I'm kidding. You don't understand sarcasm," Trump said.