Vice President Biden expressed uncertainty about a potential White House bid on Thursday, saying any candidate must be ready to give "110 percent" of themselves when running to be the nation's commander in chief.

"I'd be lying if I said that I knew I was there," Biden told "The Late Show" host Stephen Colbert. "I'm being completely honest. Nobody has a right in my view to seek that office unless they are willing to give it 110 percent of who they are."

Biden also told Colbert that "I don't think any man or woman should run for president unless, number one, they know exactly why they would want to be president and two, they can look at folks out there and say I promise you have my whole heart, my whole soul, my energy, and my passion to do this."

Biden's appearance on the nationally televised CBS show coincided with a trip to New York for events promoting a raise in the minimum wage and a White House push to increase awareness of testing for rapes. The interview was largely serious and Biden appeared emotional as he spoke about the recent death of his son, Beau, from brain cancer. He revealed that he has at times felt self-conscious about the outpouring of sympathy from the public for his loss.

"It's a little embarrassing. So many people who have losses as severe or maybe worse than mine and don't have the support I have," Biden said.  Later, he added: "The loss is serious and it's consequential, but there are so many other people going through this."

Beau's death has been cited at times as a factor that could convince Biden not to run, as he tends to his family's emotional needs, but also as a potential motivating factor for a final shot at the White House. Beau reportedly urged his father to give it a shot.

On the show, Biden recalled Beau telling him: "Dad, I know how much you love me. Promise me you're going to be all right."

Colbert asked Biden, a devout Catholic, about his faith, and the vice president said he has taken solace in being able to attend Mass and feel, in the crowd at church, a sense of being alone with his thoughts and emotions. He  said that his wife, Jill, tapes notes to the bathroom mirror, including one from Kierkegaard, the philosopher, which said: "Faith sees best in the dark."

He related an expression from his mother that "as long as you are alive you have an obligation to strive, and you're not dead until you see the face of God."

"No one owes you anything," Biden said. "You gotta get up. And I feel like I was letting down Beau, letting down my parents, letting down my family, if I didn't just get up."

The vice president empathized with Colbert, whose own father and two brothers were killed in an airplane crash.

"I marvel at the ability of people who absorb hurt and just get back up," he said. "You're one of them, old buddy. Losing your dad when you're a kid. It's like asking what made your mother do it every day?"

Colbert interjected: "She had to take care of me."

Biden replied, "I imagine that would be a hell of a job."

This post, originally published at 8:15 p.m. Thursday, has been updated.