President Joe Biden apologized to other world leaders on Monday for the Trump administration's decision to exit the Paris climate agreement, saying during the United Nations' climate summit that the US' exit put the country behind in its climate goals.

"I guess I shouldn't apologize, but I do apologize for the fact that the United States -- the last administration pulled out of the Paris accord. It put us sort of behind the eight ball a little bit," the President said during a session on "action and solidarity" at the summit in Glasgow.

The President announced the US would rejoin the Paris accords hours after he was sworn into office in January.

During the session, Biden also said "the American people, four or five years ago, weren't at all sure about climate change, whether it was real."

"Well, they have, as they say in southern parts of my state, 'seen the lord.' They've seen what's happened back home. The incredible changes that are taking place. And they're now finally … seeing the sense of urgency that you all are," Biden continued.

In his earlier opening remarks at the summit, Biden issued a plea and a warning to global leaders to take forceful action on climate change, even as his own climate ambitions hang in the balance.

"Right now, we're still falling short. There's no time to hang back, sit on the fence or argue amongst ourselves," Biden said. "This is the challenge of our collective lifetime -- the existential threat to human existence as we know it. And every day we delay, the cost of inaction increases. So let this be the moment that we answer history's call here in Glasgow."
The President said "the eyes of history upon us," adding, "We only have a brief window before us to raise our ambitions and to raise to meet the task that's rapidly narrowing. This is a decisive decade in which we have an opportunity to prove ourselves."

Biden, who is hoping to galvanize other countries to take steps in reducing emissions and keeping global temperature rise in check, told the group, "We can keep the goal of limiting global warming to just 1.5 degrees Celsius within our reach if we come together. If we commit to doing our part with each of our nations with determination and with ambition." He said the Glasgow summit "must be the kickoff of a decade of ambition and innovation to preserve our shared future."

During the summit, the US will announce "new initiatives to demonstrate our commitment to provide innovative solutions across multiple sectors," including agriculture, oil and gas, and combating deforestation, Biden said. The US will will also reveal a long-term strategy, submit a new adaptation communication, and launch a pledge with the European Union to reduce methane emissions by at least 30% by the end of the decade.

The President also detailed the current efforts in his social safety net and infrastructure proposals aimed at addressing the climate crisis, reasserting his frequent point that, "when I talk to the American people about climate change, I tell them it's about jobs."

Democratic lawmakers in Washington are continuing to debate a final package that includes more than $500 billion in climate change provisions. He told the audience the United States wouldn't shirk from its responsibilities, saying his framework would provide "historic investments in clean energy."

"It's about workers who will lay thousands of miles of transmission lines (for a) clean, modern, resilient power grid. The auto workers who build the next generation of electric vehicles. And electricians who will install a nationwide network of 500,000 vehicle stations to power them throughout my country. The engineers who will design new carbon capture systems, and the construction workers who will make them a reality," he added.

Biden called addressing climate change "a moral and economic imperative" and in the "self interest" of all nations. He also argued that recent volatility in energy prices are "a call to action" to diversity sources of power.

The President arrived in Glasgow Monday morning and has several events lined up throughout the day, including a meeting with the President of Indonesia Joko Widodo and an afternoon reception with United Kingdom Prime Minister Boris Johnson.

Just prior to delivering his speech Monday morning, Biden, who has been traveling overseas for days, was seen closing his eyes for an extended period of time and rubbing his eyes during the summit's opening session.