Opening a pre-COP leaders' summit in the Amazonian city of Belem, Lula lashed out at "extremist forces (that) fabricate fake news...to obtain electoral gains and imprison future generations," as he warned that the window to prevent calamitous climate change was "closing rapidly."

Lula pointed to a recent UN report that found Earth will likely be 2.5 degrees Celsius warmer by 2100 from pre-industrial levels.

This would claim an estimated 250,000 lives per year and shrink global GDP by almost a third, he told dozens of leaders gathered in Belem.

"Now is the moment...to face reality and decide if we will have the courage and the necessary determination to transform things," the president urged.

But he pointed to a tendency of "selfish immediate interests" prevailing over the long-term common good.

Global climate efforts have been tarnished by "insecurity and mutual mistrust," said Lula, who has been involved in a heated tariff spat with counterpart Donald Trump of the United States, which was absent from the high-level climate talks.