The last time an American secretary of state visited China her name was Madeleine Albright and she was welcomed as an old friend.

When the current US Secretary of State Colin Powell steps off his plane in Beijing on Saturday he will no doubt be given the same courtesies.

But the atmosphere will be fundamentally different.

The first few months of the Bush administration have put relations between these two giants through their toughest test in years.

Tough talk

Almost immediately he arrived in the White House President Bush began talking tough on China. President Clinton liked to refer to China as a strategic "partner". President Bush changed that to strategic "competitor".

The strategic competition

In Beijing, President Bush's plans to build a National Missile Defence system were seen as aimed directly at neutralising China's own small nuclear missile force.

Most importantly, President Bush signalled a shift in US policy towards Taiwan, which China still regards as a renegade province.

First the president promised to increase the quantity and quality of weapons sold to Taiwan, then he appeared to promise that America would help to defend Taiwan if it were attacked by China.

Then there was the spy plane collision over the South China Sea, and an 11-day stand-off in which the 24 American aircrew were effectively held hostage by China while it demanded a US apology.

It was the lowest point in relations since the Nato bombing of China's embassy in Belgrade in 1999.

Taking stock

The spy plane crisis appears to have made both sides sit back and take stock.

After two days of angry demands for his crew to be released, President Bush suddenly turned quiet and diplomatic. Beijing, while continuing its angry rhetoric, ultimately settled for much less of an apology than it had wanted.

The spy plane row left relations at their lowest for two years

Since then the rhetoric coming from both sides has been markedly less hostile. China howled with anger when the US went ahead with its promised arms sales to Taiwan, but did nothing.

Washington too has been talking more positively about its relationship with China. Secretary of State Powell may have much to do with the change of tone.

He is reported to have taken the lead in halting the angry rhetoric and forging a diplomatic solution during the spy plane row.

No bed of roses

Eager to make his visit a success, China has even gone as far as releasing three American-based academics convicted of spying on China.

That does not mean that everything is now a bed of roses.

Deep divisions remain, not least on National Missile Defence and China's human rights record.

Several other US residents remain in Chinese custody, and two years on, China's brutal suppression of the Falun Gong religious sect continues unabated.

But there does appear to be a realisation on both sides that this is a relationship that is too important to be allowed to drift in to acrimony.

And while President Bush continues to talk tough there is perhaps an acceptance in the new White House that, as one American academic put it, "if you treat China as an enemy it will become an enemy".

That is something nobody wants.