Failed Democratic presidential candidate Hillary Clinton reportedly apologized to former President Barack Obama after conceding to President Donald Trump on election night.

Shattered: Inside Hillary Clinton's Doomed Campaign by Jonathan Allen and Amie Parnes was released on Tuesday, detailing "How Hillary Clinton lost the 2016 election to Donald Trump is the tragic story of a sure thing gone off the rails."

The book revealed that Hillary Clinton "softly" apologized to then-President Obama on the election night after he called to urge her to concede, according to a Washington Post book review.

According to Allen and Parnes, Obama pressured Clinton to concede first through White House political director David Simas, who called Clinton's campaign manager Robby Mook.

"POTUS doesn’t think it’s wise to drag this out," Simas said.

When Clinton continued to wait, Obama called her himself to urge her to concede. He then repeated the message to Clinton's campaign chairman, John Podesta.

"You need to concede," Obama said.

Clinton then conceded to Trump over the phone, saying, "congratulations Donald." Just a short time later Obama was back on the phone with Clinton.

"Mr. President," Clinton said. "I’m sorry."