With days left to meet the deadline for an international deal on climate change, Secretary of State John F. Kerry issued a call to action Wednesday, saying the U.S. would double its contribution to help vulnerable nations adapt to global warming, and urging other countries to do their part to confront the problem.

Two weeks of talks outside Paris, the culmination of years of effort by the United Nations to strike a deal to fight climate change by reducing greenhouse gas emissions, are scheduled to wrap up Friday.

"If we just continue down the current path, with too many people sitting on their hands, waiting for someone else to take the responsibility, guess what, the damage is going to increase exponentially," Kerry said. “To cut to the chase: Unless the global community takes bold steps now to transition away from a high-carbon economy, we are facing unthinkable harm to our habitat, our infrastructure, our food production, our water supplies, and potentially to life itself."

Rising global temperatures already pose “an existential threat” to some countries, including small islands in danger of disappearing because of rising sea levels, Kerry said. “We are prepared to do our part, and we will not leave the most vulnerable nations among us to quite literally weather the storm alone.”

He said the United States would in the next five years double the grants it provides for climate adaptation, currently worth more than $400 million a year. The funds are part of a previously agreed commitment by wealthy nations to mobilize $100 billion a year by 2020 to help developing countries cope with global warming and transition their economies to solar, wind and other clearer energy sources.

But he said developing nations would also need to contribute to the extent they can to raise the necessary funds and reduce global emissions.

"Make no mistake: If a global community cannot come together and refuses to rise to this challenge — if we continue to allow calculated obstruction to derail the urgency of this moment — we will be liable for a collective moral failure of historic consequence," Kerry said. “That’s why we need to act within the next 36 to 48 hours. We need to get the job done.”