All is not well between Donald Trump and Jerry Seinfeld. The comedian reportedly pulled out from an event appearance and Trump called him out in an open letter.

According to Page Six, Seinfeld was scheduled to attend a Sept. 13 event for St. Jude Children's Research Hospital and the Eric Trump Foundation. However, he has since canceled his appearance due to Trump's negative remarks about President Obama.

"I just learned you canceled a show for my son's charity," Trump wrote to Seinfeld, "because of the fact that I am being very aggressive with respect to President Obama, who is doing an absolutely terrible job as our leader."

Trump, who is considering a 2012 presidential run, didn't stop reprimanding the comedian there.