Canadian Prime Minister Justin Trudeau highlighting Washington's return to the front lines of the fight against man-made climate change, the two-day summit starting Thursday will be the first big event on the environment of his presidency and comes ahead of two other major climate meetings later in the year.
"There's no question that we need a country of the scale of the United States to be part of the solution, not part of the problem if we're going to make it as a planet," he said.
World leaders gathered virtually for an international climate summit convened by US President Joe Biden, in which they vowed to meet or ramp up their goals to reduce emissions and slow global warming.
The US president, seeking to urge emerging economies into action on addressing the climate emergency, also said that by 2024 Washington will double its annual public financing commitments to developing countries.
One day before the summit, Europe effectively set in stone its commitment to make the continent climate neutral by 2050, European Commission president Ursula von der Leyen told the world leaders.
President Xi Jinping reiterated his pledge that China -- by far the world's largest emitter -- would reach carbon neutrality "before 2060."
Putin said the world's fourth-largest greenhouse gas emitter had set out to "significantly limit" net emissions by 2050.