U.S. President Donald Trump said on Sunday that if he could have one "do-over," it would be "personnel" decisions, including naming former Sen. Jeff Sessions as his first U.S. attorney general.

"I would say if I had one do over, it would be, I would not have appointed Jeff Sessions to be attorney general. ... That was the biggest mistake," Trump said in an interview aired on Sunday with NBC's "Meet the Press" program.

After almost three years of investigations, Trump's presidency is still clouded by questions surrounding Russian interference to boost his candidacy in the 2016 U.S. elections and his subsequent efforts to impede inquiries into the matter.