Barack Obama got a global standing ovation long before he was elected president of the United States.

Barack Obama got a global standing ovation long before he was elected president of the United States.

But in a fickle and fast-moving world, the overseas reviews are already turning mixed.

Though much of the world will party through tonight after Obama is sworn in as America's 44th president - just as it did when he was elected - there are signs the ardour is cooling as the sheer weight of his challenges sinks in.

A deepening global recession, new hostilities in the Middle East, complications in closing the Guantanamo Bay prison, Iran, North Korea, Afghanistan - an impatient world has a stake in all of them and is asking how much change Obama can deliver.

"Just two months ago, the future president seemed a cross between Superman and Merlin the magician," Massimo Gramellini wrote in Italy's La Stampa newspaper.

"Now he himself admits he won't be able to keep all his promises, and who knows? Maybe someone will ask for his impeachment by the end of next week."

"The idealism has diminished," said Samuel Solvit, who heads an Obama support network in France. "Everyone was dreaming a little. Now people are more realistic."

Muslims want to know why Obama hasn't joined the chorus of international criticism of Israel's Gaza offensive.

Last week posters of him were set on fire in Tehran to shouts of "Death to Obama!"

"By the time Obama takes office, hundreds or thousands more will be killed in Gaza and it will be too late for him to act," said Adel Fawzi, an Egyptian government clerk in Cairo.

Obama has expressed concern about Gaza, but says he's reluctant to say much more until his inauguration.

Meanwhile, the global economic collapse is already closing in on him. Around the world, leaders and their publics are waiting to see what he does to calm roiled markets and restore confidence.

British prime minister Gordon Brown and German chancellor Angela Merkel both say they're confident the Obama administration will succeed in working with Europe and China to build a stronger global economy.

"He has a big vision of how America can contribute to the long-term prosperity of the world," Brown said.

"The chances of us working this out are good," Merkel said in Berlin, where Madame Tussauds rolled out a wax likeness of Obama to great fanfare.

Sweden's prime minister, Fredrik Reinfeldt, told parliament last week he empathises with the monumental challenges facing Obama.

"I think it's difficult to find an American president who is being met with such a number of expectations as Barack Obama."

That's the problem, said Reginald Dale, a senior fellow at the Center for Strategic and International Studies in Washington: People everywhere simply expect too much, practically ensuring Obama will disappoint.

"The United States can't solve all the world's problems," he said.

"It does not have enough money or military power. And the president is constrained by Congress and the constitution."

Dozens of developing countries rely on US foreign aid. But an administration preoccupied with keeping Americans from losing their homes and jobs may have to cut back on foreign aid.

Even items on Obama's agenda that initially seemed straightforward are turning out to be fraught with complications, such as closing Guantanamo in eastern Cuba.

Obama has hinted that it may be his first executive order - but experts say it could take a year to accomplish.

"There are all sorts of logistical questions," Dale said. "What if they suddenly captured Osama bin Laden? Where would they put him? It's very easy for people abroad to take these issues as symbols of what they think is wrong with America. They need to understand the Americans don't like these things any more than they do."

That hasn't stopped US critics like Venezuelan president Hugo Chavez from offering advice.

"I don't want to tell President Obama what to do," Chavez said. He did anyway: If Obama wants to free up billions of dollars, Chavez said, he should pull US troops out of Iraq immediately and shrink Washington's military bootprint around the world.

Obama did pledge during the campaign to withdraw all American combat forces from Iraq within 16 months of taking office. But he also vowed to shift the focus to Afghanistan - and Obama's Pentagon is likely to find it hard to persuade allies to commit more troops there.

Mexico has tempered its expectations that Obama will bring "transformational change" to the economy or quickly tackle immigration reform. As Agustin Carstens, Mexico's treasury secretary, put it: "At the end of the day, we have to be realistic."

All the same, there's still plenty of Obamamania overseas, particularly in Europe, where George Bush is unpopular.

"We still have high expectations," said Dean Cole, selling fruit from a north London market stand. Obama "strikes me as a man of honour".

Maria Gabriella Lunato, a salesman in Rome, Italy, reveres Obama as though he were a pope.

"He will not be just an American president, but a person who will spread justice around the world," she said.

But Lise Lindeberg, a retiree in Stockholm, Sweden, thinks people have put too much faith in Obama. "I feel sorry for the poor thing," she said.

"People want him to be a saviour. You just can't become president and change everything when there's no money." - Sapa-AP