In pictures: US-China relations

President Barack Obama arriving in Beijing, 16 November 2009

After Barack Obama landed in China on his first trip as US president, he noted that relations between the two countries had "not been without disagreement and difficulty". Here is a look at other visits, and the diplomatic tensions that surrounded them.

Members of the US table tennis team land in Tokyo after a week in China, 17 April 1971

The US only established diplomatic ties with communist China in 1979. In 1971 it was left to a US table tennis team - seen here landing in Tokyo after a week in China - to make a "ping pong diplomacy" visit that helped lead to a warming of relations.

Chairman Mao Zedong welcomes US President Richard Nixon at his home in the Forbidden City in Beijing, 22 February 1972

That, along with a secret visit by Secretary of State Henry Kissinger, helped set up a historic trip by President Richard Nixon - pictured here being welcomed by Chairman Mao to his Beijing home in February 1972.

On left, George H W Bush with his wife Barbara in Beijing, 1974; On right, the couple in Beijing on 25 February, when Mr Bush was visiting as US president

In 1974-5, with Mao Zedong still in power, George H W Bush was posted to Beijing as US envoy. He was back in Tiananmen Square as president in February 1989, just months before hundreds were killed there in protests.

Then-US President Bill Clinton on the Great Wall of China with his wife Hillary and daughter Chelsea, 28 June 1998

President Bill Clinton accused his predecessor of "coddling" China's leaders, but did eventually drop his policy of linking human rights reform to the annual renewal of China's Most Favoured Nation trading status. He visited China with his family in 1998.

On left, Chinese pilot Wang Wei standing in the cockpit of a jet in an undated photo; on right, then-US president George W Bush in a traditional Chinese coat talks to then-Chinese President Jiang Zemin in Shanghai, 21 October 2001

Relations soured again when a US spy plane hit a Chinese fighter jet and made an emergency landing in Hainan in 2001. China freed the crew only after President George W Bush said he was "very sorry" that Chinese pilot Wang Wei had died in the incident.

US President Barack Obama greets students in Shanghai, 16 November 2009

President Obama said there was no reason the US and China - a "majestic" country - should not co-operate. But he also made comments less likely to be welcomed by his hosts, telling students that certain freedoms were "universal rights".