Top polluters Washington and Beijing announced a groundbreaking agreement yesterday to make serious efforts to combat global warming.

The US set an ambitious new goal to stop pumping as much carbon dioxide into the air, while China agreed for the first time to a self-imposed deadline of 2030 for emissions to peak.

Dual announcements in Beijing by US President Barack Obama and Chinese President Xi Jinping (pictured) came as a shock to environmentalists who had hoped with no real confidence for such action.

Mr Obama’s Republican opponents in Washington accused Mr Obama of dumping an unrealistic obligation on the next president.

US officials said that Secretary of State John Kerry had floated the idea during a visit to China in February and that Mr Obama had followed up by writing to Mr Xi in the spring to suggest that the world’s two largest economies join forces.

The two countries finally sealed the deal late on Tuesday, just in time to announce it as the US president’s trip to China came to an end.

“This is a major milestone in the US-China relationship,” said Mr Obama, with Mr Xi at his side.

“It shows what’s possible when we work together on an urgent global challenge.”

Under the agreement, Mr Obama set a goal to cut US emissions by between 26 and 28 per cent by 2025, compared with 2005 levels.

Officials claim that Washington is already on track to meet the president’s earlier goal to lower emissions by 17 per cent by 2020 and that the revised goal means that the US would have to cut pollution roughly twice as quickly during a five-year period starting in 2020.

China, whose emissions are growing as it builds new coal-fired power plants, set a target for its emissions to peak by about 2030 — earlier if possible — with the idea being that its emissions would then start falling.

Although that goal still allows China to keep pumping more carbon dioxide for the next 16 years, it marked an unprecedented step for Beijing, which has been reluctant to be boxed in by global climate concerns.