joe biden
Vice President Joe Biden, in a PBS interview, told President-elect Donald Trump it's time to be an adult now that he's president. Above, Biden speaks during an official dinner at the Sir John A. MacDonald Building in Ottawa, Ontario, Canada, Dec. 8, 2016. Chris Wattie/Reuters

Former Vice President Joe Biden said Thursday that President Donald Trump needs to "grow up" and "stop tweeting." Biden made the comments at an event to launch the Penn Biden Center for Diplomacy and Global Engagement at the University of Pennsylvania.

During the event, a student asked him, "If you could give president Trump one piece of advice what would it be?" In response to this, Biden said, "Grow up." He also mentioned that if he would have been the president of the United States, "I would stop tweeting and start focusing."

"The words of a president matter. They have enormous, enormous, enormous, reverberating sounds around the world. Every time a U.S. president speaks and says something, leaders and people around the world try to dissect what he means because it matters so much to their security, threats they face, whatever it is. So, you can't loosely make assertions without limiting your ability to lead," Biden added, CNN reported.

Read: Joe Biden To Hold New Position At Donald Trump's Alma Mater

Biden also suggested that the president needs to get his strategies right and that he should lead the country by setting an example. He expressed his concerns about the direction in which the Trump administration was taking the country. He added that he was worried about tax reforms because he believed the Republicans won't be successful.

"One of the reasons I predict there will be no tax bill is there's not enough people in the Treasury to handle the calculations and strategy. I was told at least three weeks ago you could walk down the halls of the State Department and holler and no one would hear you," he joked, "because no one was there."

"I mean that in substantial part because, in fairness to Trump, I don't believe Trump ever thought he would be President Trump. I don't think he thought he was going to be president," Biden said, referring to the time when Trump supported Biden's Democrat nomination for the Senate.

"I think that by the time it got around to realizing he just might win, he had not taken the time ... to put together a transition team. ... And so he was at an enormous disadvantage when he won," he added, according to the Hill.

Biden also indirectly mocked Hillary Clinton's unsuccessful presidential campaign saying that Clinton could not actually appeal to the middle class, which made her lose the votes.

"What happened was that this was the first campaign that I can recall where my party did not talk about what it always stood for -- and that was how to maintain a burgeoning middle class. You didn't hear a single solitary sentence in the last campaign about that guy working on the assembly line making $60,000 bucks a year and a wife making $32,000 as a hostess in restaurant," he said, according to CNN.