KATOWICE, Poland — The United Nations secretary-general called on countries to make compromises in tackling global warming, amid concern that the U.N. conference on the issue could end without a substantial agreement.

In his second dramatic appeal at the talks in Poland in the space of 10 days, Antonio Guterres told ministers and senior diplomats from almost 200 countries they should consider the fate of future generations.

“This is the time for political compromises to be reached,” he said. “This means sacrifices, but it will benefit us all collectively.”

His call came as the two-week meeting in Katowice shifted from the technical to political phase, with ministers taking over negotiations.

Campaign groups warned of the risks of failure and accused powerful players such as the European Union of not pushing hard enough to reach an agreement.

“A new leadership must step up,” said Vanessa Perez-Cirera of the environmental group WWF. “We cannot afford to lose one of the 12 years we have remaining.”

She was referring to a recent scientific report by a U.N.-backed panel that suggested global warming can only be capped at 2.7 degrees Fahrenheit if urgent action is taken by 2030, including a sharp reduction in use of fossil fuels.

The U.S., Russia, Saudi Arabia and Kuwait have opposed endorsing the Intergovernmental Panel on Climate Change report.