A coalition of activists from around the globe on Tuesday called for the postponement of a major United Nations climate summit this fall in Scotland, saying a combination of vaccine inequity, exorbitant lodging costs and the ongoing coronavirus pandemic could exclude important voices — particularly those of people from small and developing nations hit hardest by global warming.

The call to delay the crucial meeting came as the heads of the Catholic, Orthodox and Anglican churches made an unprecedented joint declaration urging world leaders to tackle climate change, with special attention paid to how a warming world will hurt the planet’s most vulnerable people.

With just seven weeks to go, British officials scrambled to keep the global negotiations on track, amid continued deep divisions among economic powers on how to reduce emissions of greenhouse gases. Uncertainty over the future of the pandemic — and who will show up at the U.N. climate conference in Glasgow — adds further obstacles to a summit that has been called a moment of truth for planetary health.

To calm calls for postponement, the British government has announced help with quarantine costs and vaccinations for delegates from countries with high rates of coronavirus infections.

According to the activists, the danger is that those countries “most deeply affected by the climate crisis and those countries suffering from the lack of support by rich nations in providing vaccines will be left out of the talks and be conspicuous in their absence,” Tasneem Essop, executive director of the Climate Action Network, a collection of hundreds of nonprofit and nongovernmental advocacy groups across 130 countries, said in a statement.

“There has always been an inherent power imbalance within the UN climate talks, and this is now compounded by the health crisis,” she added.

Greenpeace joined the push Tuesday to delay the global climate negotiations, saying that Britain, as the host nation, has failed to guarantee “the safe and equitable participation” of delegations from around the world, especially those battered by both covid-19 and climate-fueled disasters.

“Expecting already disadvantaged people to attend without access to vaccines, healthcare, and financial support to overcome the risks of participation, is not only unfair but prohibitive,” Juan Pablo Osornio, senior political lead for Greenpeace International, said in a statement.

The Union of Concerned Scientists also supported a postponement, saying the conference as currently planned “cannot meet science-based public health guidelines in an equitable way.”

Top British officials, as well as leaders in other countries, have insisted that the climate summit scheduled for Glasgow in November must move forward, given the urgent need for the world to move swiftly and cooperatively to combat climate change.

To safeguard the conference, and in response to calls for a delay, the British government on Tuesday announced additional help for delegates, offering to pay the costs of those required to quarantine in hotels upon arrival because they are traveling from “red list” countries with high coronavirus infection rates.

Earlier, British Prime Minister Boris Johnson promised to work with the United Nations to deliver coronavirus vaccines to all delegates, official observers and accredited journalists who could not receive doses in their home countries. British officials, criticized for a slow start, said Tuesday that the vaccines are now being shipped and that the first doses are scheduled to be given to delegates by the end of the week.

Alok Sharma, the British minister serving as president-designate of the 26th U.N. Climate Change Conference of the Parties, known as COP26, said hearing “the voices of those most affected by climate change” is a top priority for Britain.

“COP26 has already been postponed by one year, and we are all too aware climate change has not taken time off,” Sharma said in a statement. “We are working tirelessly with all our partners, including the Scottish Government and the UN, to ensure an inclusive, accessible and safe summit in Glasgow with a comprehensive set of COVID mitigation measures.”

In a joint declaration Tuesday that is the first of its kind, Pope Francis, head of the Roman Catholic Church; Ecumenical Patriarch Bartholomew I of Constantinople, the spiritual leader of the Orthodox Church; and the Archbishop of Canterbury, Justin Welby, leader of the global Anglican Communion, called on world leaders to “listen to the cry of the Earth and of people who are poor.”

“We stand before a harsh justice: biodiversity loss, environmental degradation and climate change are the inevitable consequences of our actions, since we have greedily consumed more of the Earth’s resources than the planet can endure,” they wrote.

The three men called on individuals “to make meaningful sacrifices for the sake of the planet, working together and taking responsibility for how we use our resources.”

“This is a critical moment. Our children’s future and the future of our common home depend on it,” they warned.

Already, the world has warmed more than 1 degree Celsius (1.8 Fahrenheit) since preindustrial times, with few signs of slowing. Six years ago in Paris, the world made a collective pact to limit warming to “well below” 2 degrees Celsius (3.6 Fahrenheit). But global greenhouse gas emissions have continued to rise, and the world remains on a troubling trajectory.

Last month, the Intergovernmental Panel on Climate Change released a searing, 4,000-page report on the current state of climate science, detailing how humans have altered the environment at an “unprecedented” pace and making clear that more catastrophic impacts lie ahead without rapid cuts in emissions.

On Sunday, editors of more than 200 medical journals, including the New England Journal of Medicine and the Lancet, called climate change “the greatest threat to global public health.”

As envisioned, COP26 is the very definition of a mass gathering. British officials have said they expect roughly 25,000 official attendees from more than 190 countries to descend on the Scottish Event Campus in downtown Glasgow, which during the pandemic was staged as an emergency hospital and served as a coronavirus vaccination site.

The climate summit — already delayed a year by the pandemic — has been billed as a moment of truth, when leaders from nearly 200 countries would enshrine the bold commitments to cut carbon emissions that scientists say are essential to put the world on a less disastrous path.

But the raging pandemic has created a logistics nightmare surrounding the event, which typically draws government negotiators, researchers, elected leaders, environmental activists, industry representatives and protesters from every part of the globe.

A spokesperson for the British government said that it was “on track to support all those registered to be vaccinated ahead of the summit” and that it plans to start administering first doses of the Oxford-AstraZeneca vaccine by week’s end.

In Britain, the AstraZeneca vaccine is given in two doses, with an interval of eight weeks between shots. For the climate summit delegates, that interval must be shortened to four weeks between first and second shots, giving them barely enough time to reach full immunity before the summit starts.

Still, questions remain about whether such doses will get distributed in time to delegates in dozens of nations, some where overall vaccination rates remain in the single digits. Even then, representatives from small, poorer nations face high travel and lodging costs. Glasgow hotels are charging sky-high room rates, in many cases quadrupling prices.

Swedish climate activist Greta Thunberg, a star at past U.N. climate gatherings, has held out the possibility that she may not attend COP26 unless it is “safe and democratic.” She told BBC Scotland last week that meant ensuring participants from poorer countries are fully vaccinated and able to travel.

British officials have said they would make an exception to allow delegates from covid red-list countries to enter to attend COP26. Yet, according to the latest protocols, even if fully vaccinated, those participants from the 60 red-list nations must still quarantine at a government-sanctioned hotel for five days. Those not fully vaccinated must spend twice that long in quarantine.

“If COP26 goes ahead as currently planned, I fear it is only the rich countries and [nongovernmental organizations] from those countries that would be able to attend,” Mohamed Adow, director of the Nairobi-based think tank Power Shift Africa, said in a statement. “This flies in the face of the principles of the U.N. process. … A climate summit without the voices of those most affected by climate change is not fit for purpose.”

As activists and organizers alike wrestle with the thorny details of how to proceed this fall in Scotland, they face a series of unenviable and imperfect choices. But on this much they seem to agree: Time is running short to meet the central goals of the Paris agreement.

“Regardless of whether the COP goes ahead, ambitious action on climate is urgently needed,” Osornio said, adding: “The longer governments delay to honor their Paris climate commitments, the harder it will be.”

Booth reported from London.