Cop26 must go ahead in person, the event's president Alok Sharma said on Friday, as fears mount that delegates will pull out due to coronavirus concerns.
The 26th edition of the UN Climate Change Conference of the Parties marks the biggest climate summit since the 2015 Paris Agreement.
Negotiators from 196 countries and the European Union, along with businesses, experts and world leaders, are set to travel to Glasgow in Scotland for the scheduled start on November 1.
This may be easier said than achieved. Contradictory and confusing Covid travel rules make globetrotting a circuitous undertaking; new variants and mutations pose a compounding risk of vaccine evasion, and some fear the UK itself may be in the early stages of a third wave.
Alok Sharma is not considering hosting the event online, however.
"We need to have a physical event. We cannot allow any further delay," he told AFP.
"We've already delayed Cop by one year and I'm afraid that during that year climate change has not abated. In fact, last year was the hottest year on record, the last decade was the hottest on record."
"We are looking at all Covid-secure measures, including vaccines, to deal with this particular issue", he said.
Nations around the world committed under the 2015 Paris accord to keeping the global temperature increase to under 2°C, and ideally closer to 1.5°C, by 2050.
The upcoming talks are crucial to meeting the target.
"This is going to be the decisive decade. And we have to act now," said Mr Sharma, after flying to Dhaka, Bangladesh, to discuss the coal-reliant nation's transition to clean energy.
"All countries need to come forward, set out ambitious plans to cut their emissions, but also to be carbon neutral, to be net-zero emissions by the middle of the century."
In a special report released in May, the International Energy Agency said all inefficient coal power plants needed to close by 2030 in order to reach net-zero emissions.
"I have been very clear that I want coal power to be consigned to history," Mr Sharma said.
"The clean energy transition, of course, is going to be vital, not just for Bangladesh but indeed for countries around the world."