US envoy John Kerry on Tuesday (20) said that the world cannot wait for the Covid-19 pandemic to end before dealing with climate change.
He stressed how "pivotal" this year's UN climate conference was to press ahead with action.
Addressing an audience at London's Royal Botanic Gardens, Kerry said nations must step up at the summit, COP26, to not only meet the pledges made six years ago in the Paris agreement, but to go beyond them.
COP26, to be held in Glasgow, Scotland, in November, is seen as a critical opportunity for countries to make more ambitious commitments to achieve net-zero emissions by 2050 and keep the global average temperature rise to 1.5 degrees Celsius this century, which was set under the Paris Agreement in 2015.
"I am very sorry to say, the suffering of Covid will be magnified many times over in a world that does not grapple with, and ultimately halt, the climate crisis," he told an event hosted in partnership with think tank Chatham House.
"We don't have the luxury of waiting until Covid is vanquished to take up the climate challenge."
Since US President Joe Biden announced his country's return to the Paris Agreement earlier this year, Kerry has been active in trying to restore US leadership in combating global warming, and he called on countries to make COP26 a pivotal summit.
After being postponed last year due to the coronavirus pandemic, the summit will be the first time nations will review their climate targets and try to strengthen them.
But current countries' plans put the world on track for a 2.4 degrees C average temperature rise by the end of the century, according to analysis by Climate Action Tracker.
"(The world) must make COP26 in Glasgow, this year, a pivotal moment for the world to come together to meet and master the climate challenge," Kerry said.
"After our absence for four years, my friends, we approach this challenge with humility. But let me be clear, we approach it with ambition."