The United States and China are to set up a joint working group on climate change and have a shared view on the "increasing dangers" of global warming.
The two countries "recognise that the increasing dangers presented by climate change measured against the inadequacy of the global response requires a more focused and urgent initiative", they said in a statement issued in Beijing on Saturday.
The initiative came as US Secretary of State John Kerry visited Beijing for talks with top leaders focused largely on the nuclear crisis on the Korean peninsula.
But the issue of how to deal with climate change has long vexed relations between the world's two biggest economies, which are also the biggest emitters of greenhouse gases.
China says developing countries, which emit far less carbon per capita, should not have to bear the same burden as advanced economies in tackling the problem.
"By agreeing to raise the issue of climate change and energy policy to the ministerial level … we put on an accelerated basis at a higher level our joint efforts with respect to energy and climate," Kerry said.
"And I think that globally that will be a very significant step and significant message."
State Councillor Yang Jiechi , the nation's top foreign policy official, said the two sides would "strengthen practical cooperation" in areas including the economy, energy and environmental protection.
In the joint statement, Beijing and Washington said they "took special note of the overwhelming scientific consensus" concerning "climate change and its worsening impacts".
Those included rising global temperatures, rapid melting of Arctic sea ice and "the striking incidence of extreme weather events occurring all over the world", they said.
Both sides "recognise that the increasing dangers presented by climate change measured against the inadequacy of the global response requires a more focused and urgent initiative", according to the statement.
Also, Yang and Kerry pledged to deepen Sino-US co-operation in clean energy, after attending a China-US energy co-operation seminar in Beijing on Saturday evening.
As the world's top energy producer and consumer, the US and China shared broad common interests in the fields of clean energy, energy conservation and environmental protection, Yang said. During Kerry's visit, the two countries had reached broad consensus on deepening bilateral co-operation in these areas, he added, urging both sides to make contributions to world energy safety and coping with climate change.
Kerry suggested that the two sides should enhance dialogue and deepen co-operation in clean energy, to promote energy conservation globally and create more opportunities for business and employment.