Almost 35 years after U.S. President Richard Nixon startled the world by visiting China, the boldness of the trip and his meeting with Mao Zedong still capture the imagination.

The week-long visit in February 1972 has often been portrayed as a remarkable success that allowed a U.S. president to repair ties with China, put pressure on the Soviet Union and help ease Washington's path out of the Vietnam War.

"This was the week that changed the world," Nixon declared at the end of the visit.

But prominent Canadian historian Margaret MacMillan -- author of a new book on the event -- suggests the Americans gave too much away to Beijing, only achieved mixed results and sowed the seeds for China's formidable economic rise.

The United States had refused to recognize China after 1949, and bilateral ties had been icy for years.

By the end of the 1960s, however, both nations needed each other. A diplomatically isolated and backward China, trying to recover from the disastrous reforms known as the Cultural Revolution, fretted about a possible attack by the neighboring Soviet Union.

The United States, also worried about Moscow, wanted to boost its position in Asia and hoped China could help persuade North Vietnam to call a halt to hostilities. So Nixon reversed two decades of official policy and went to Beijing.

Although the hour-long talk between Nixon and Mao rarely went beyond generalities, the meeting was hugely significant.

"It was an earthquake in the Cold War landscape and meant the Eastern Bloc no longer stood firm against the West," MacMillan writes in "Nixon in China."

MacMillan, author of the best-selling book "Paris 1919", says Washington took a huge risk before Nixon's trip.

As part of a bid to show good faith, national security adviser Henry Kissinger gave China reams of secret U.S. spy data on the Soviet Union.

"They came rather as supplicants to the Chinese and they handed over huge amounts of intelligence and I think they left the Chinese with the impression that really the Americans needed them more than the Chinese needed the Americans," MacMillan told Reuters in an interview.

In truth, the Chinese desperately needed help to escape what China's State Information Minister Cai Wu calls the chaos of the Cultural Revolution.

"Nixon's visit opened a door at that time for China to the rest of the world," he said during a recent visit to Ottawa.

Almost hidden among the fanfare, banquets and media frenzy was the joint commitment to boost academic contacts as well as trade -- topics which did not interest Kissinger or Nixon.

"The maximum amount of bilateral trade possible between us, even if we make great efforts, is infinitesimal in terms of our total economy," Kissinger told deputy Chinese Foreign Minister Qiao Guanhua.

In reality, the academic visits quickly helped China build up vital knowledge and skills. And the promise of greater access to U.S. markets was crucial.

After Mao died in 1976, his successors launched economic reforms that turned China into the powerhouse that is now, running a $200 billion trade surplus with the United States. China helps keep its rival afloat by buying vast amounts of U.S. debt.

As time passed, other drawbacks of the Nixon visit became clear to Washington. Although the trip did deliver the desired shock to Moscow, it also proved an unpleasant surprise to allies such as Japan.

And despite Nixon's hopes, the China card did not result in effective pressure on North Vietnam to reach a peace deal.

Even without Nixon's visit, she feels, China and the United States would eventually have come to an understanding.

Now, as a confident China seeks to exert its influence and track down sources of raw materials, more problems seem likely with a weakened United States.

"There are areas where they are going to clash more and more. I think commodities are going to be a real problem," said MacMillan.