Former President Bill Clinton has sparked health fears after he was caught appearing to doze off during Barack Obama's public library opening ceremony. 

Clinton and his wife Hillary joined several former presidents and first ladies on Thursday at the event on Thursday in Jackson Park, Chicago. 

The celebration was jam-packed with performances and speeches and the long event appeared to take a toll on Clinton, who seemingly fell asleep on stage, directly behind Barack and Michelle Obama. 

At one point he used his hand to cradle his head, which appeared to tilt downward although his dark sunglasses shielded any view of his eyes.

The Obamas, Bidens, Bushes and Clintons all cozied up together for a group picture ahead of the dedication ceremony. 

One picture showed Michelle hugging former President George Bush while former President Bill Clinton laughed behind them.

Joe and Jill Biden, the former president and first lady, were seen in a cheeky snap blowing a kiss at the camera together.

Michelle and Barack Obama's daughters, Malia and Sasha, also came out to support their parents, waving and smiling widely at the crowd.

The event was packed with A-listers including John Legend and his wife Chrissy Teigen, former late-night talk show host Stephen Colbert, Oprah Winfrey, Tom Hanks and his wife Rita Wilson, Tyler Perry, Steven Spielberg and former fashion model Jill Vedder, among others.

California Governor Gavin Newsom, US Rep Nancy Pelosi, Illinois Governor JB Pritzker, former Prime Minister of Canada Justin Trudeau, Former White House Chief of Staff Rahm Emanuel and former Vice President Kamala Harris and her husband Doug Emhoff and more political bigwigs were also in attendance.

Jennifer Hudson sang the national anthem to kick off the event. 

President Donald Trump was not invited to the event, as the focus was on welcoming Obama supporters, Obama Foundation CEO Valerie Jarrett said, according to NBC News.

Trump is a staunch critic of the Obamas, and often slams the former president for how he handled things in the White House.

He is still welcome to visit the center in the future, Jarrett added.

Jarrett, a longtime adviser to the Obamas, made a speech that reflected on her relationship with the couple and their family.

'They were engaged to be married. Malia and Sasha were a glimmer in their eyes, and they were just beginning their careers. They didn't know what path their lives would take, but they were both committed to a life of service,' she told the crowd.

The Obama Center project plans were made public in May 2017 and originally projected to be completed by 2021.

But the COVID-19 pandemic sparked delays, along with the expansion of the center's original plans.

The campus itself sits on 19 acres of land and includes a public park, museum, library, ample green space, and an NBA regulation-size basketball court.

Approximately $850 million went into building the center, making it the most expensive presidential library in US history.

The Daily Mail has approached Clinton for comment.