US President Barack Obama and Chinese counterpart Xi Jinping have vowed to fight global warming and halt commercial cyber theft, but exchanged sharp words on human rights and territorial disputes.
At an extraordinary joint news conference, Obama chided China on its treatment of dissidents and insisted hacking attacks on US firms must stop, even as he thanked Xi for his commitment on climate change.
The world's top two economic powers are also its biggest polluters, and campaigners hailed their commitment to reduce emissions as a key step toward a global climate pact before the end of the year.
This achievement was all the more remarkable given the tensions over industrial espionage and China's aggressive moves to seize disputed territory in the South China Sea.
The red carpet and full ceremonial honours that welcomed Xi to the White House underlined the importance of the great powers' relationship, but the leaders made no effort to conceal their differences.