BEIJING - The United States and China on Wednesday announced an action plan on greenhouse emissions as part of a "historic" pact that was acclaimed by climate scientists.

At a Beijing summit, the leaders of the world's two biggest economies put their stamp on attempts to breathe new life into action against global warming ahead of international talks in Paris next year.

US President Barack Obama said the joint announcement on the two countries' emissions targets was a "historic agreement" and a "major milestone in the US-China relationship".

President Xi Jinping said: "We agreed to make sure that international climate change negotiations will reach an agreement in Paris."

In the action plan, China sets a target for its greenhouse gas output to peak "around 2030", and intends to increase the share of non-fossil fuels in primary energy consumption to around 20% by 2030.

And Obama, who faces skepticism as well as outright denial about climate change in the US Congress, set a goal for the United States to cut its own emissions of greenhouse gases by 26 to 28 percent from 2005 levels by 2025.

Both countries agreed to launching a Climate-Smart/Low-Carbon Cities Initiative. 

As a first step, China and the US will convene a Climate-Smart/ Low-Carbon Cities Summit where leading cities from both countries can share best practices, set new goals and celebrate city-level leadership in reducing carbon emissions and building resilience, according to the action plan.

"We have a special responsibility to lead the worldwide effort against climate change," Obama said at a joint news conference with Xi. "We hope to encourage all economies to be more ambitious," he added.

China and the US, which together produce around 45 percent of the world's carbon dioxide, will be key to ensuring a global deal on reducing emissions after 2020 is reached next year. The World Resources Institute, a US-based environmental group, hailed the Obama-Xi pact as a breakthrough.

"It's a new day to have the leaders of the US and China stand shoulder-to-shoulder and make significant commitments to curb their country's emissions," the institute's president Andrew Steer said in a statement.

"They have both clearly acknowledged the mounting threat of climate change and the urgency of action," he said.

The European Union pledged last month to reduce emissions by at least 40 percent by 2030 compared with 1990 levels.

The EU accounts for 11 percent of the world's greenhouse gas emissions, compared to 16 percent for the United States and 29 percent for China.

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The full text of the agreement on climate change is as follows.