COP26, the landmark United Nations climate conference of 2020 — originally planned to be held in Glasgow, Scotland, in November — will be delayed due to the coronavirus pandemic.

“The world is facing an unprecedented global challenge & countries are rightly focusing on fighting #COVID19,” wrote Alok Sharma, the president of COP26 and a member of the U.K. parliament, on Twitter. “Due to this, #COP26 has been postponed.”

Policymakers and scientists have speculated for weeks about whether the conference, which would bring together delegations from almost 200 countries around the world, would be rescheduled due to the pandemic spreading across the globe.

Some had urged decision-makers not to delay the talks, saying that COP26 was a crucial step to advancing the goals of the 2016 Paris Agreement. “If it is going to be canceled, that should only be done at the last possible minute — in October,” Yvo do Boer, a former chief of the United Nations Framework Convention on Climate Change (UNFCCC), told the Guardian in mid-March. (The UNFCCC, the UN treaty responsible for preventing dangerous climate change, is the framework for the annual COP, or “Conference of the Parties,” meetings.)

But with national governments reeling from almost 900,000 cases of coronavirus worldwide, the possibility of a successful and productive COP26 looked increasingly slim.

The conference will be held instead in 2021, but the United Nations and the U.K. have not agreed upon a new date. This is not the first COP to experience logistical problems — last year, COP25 had to be moved abruptly from Chile to Spain due to social unrest — but the disruption in this case will be much more significant.

Countries were expected to present updated national emissions targets at COP26, and there was hope that many countries would pledge to reduce their emissions to net-zero by 2050. The world is currently far off-track to meet the goals set by the almost 200 countries that signed onto the Paris Agreement four years ago.

While the coronavirus may have slowed global emissions for the moment, experts worry that the pandemic will hinder the transition from fossil fuels to renewable energy in the long run. And the COP26 delay could drive attention away from the need to reduce fossil fuel use as quickly as possible.

“COVID-19 is the most urgent threat facing humanity today,” Patricia Espinosa, U.N. executive secretary for climate change, said in a statement. “But we cannot forget that climate change is the biggest threat facing humanity over the long term.”