Washington - US Vice-President Joe Biden has a blunt suggestion for President-elect Donald Trump: It is time to "grow up".Asked about a few of Trump's controversial remarks and tweets since winning the November election, Biden had some intemperate comments of his own."Grow up Donald, grow up, time to be an adult, you're president," he told television station PBS in an interview broadcast on Thursday. "Time to do something. Show us what you have."Trump earlier on Thursday described America's leading congressional Democrat as the "head clown".Biden has indicated he will not step away from the political fray entirely when he leaves office with President Barack Obama on January 20.The vice president has already been chiming in on how Democrats should respond to their shock election defeat, suggesting a renewed focus on the working and middle class."It's going to be much clearer what he's for and against and what we're for and against," Biden told PBS.