Istanbul President Barack Obama's eight-day European tour left little doubt he plans to exploit his popular political brand and multi-cultural biography to the utmost to repair the US image abroad.

To be sure, the Obama administration, like others before it, will still act on hardnosed judgements of national interest in applying US power abroad.

And tangible gains on issues like engaging the Muslim world and nuclear arms reductions -- two main thrusts of his trip -- will also take time.

"You plant, you cultivate, you harvest, this is a longer process than a week," Obama's top political advisor David Axelrod said.

"You don't leave with the bounty in the first instance."

But Obama's personality and political skills on show in campaign-style events on the fringes of an exhausting whirl of global summits and bilateral meetings will now clearly be a key facet of US engagement abroad.

Obama said that his late father's Islamic faith and a childhood partly in Indonesia made him a very different kind of American president.

"The United States has been enriched by Muslim Americans," Obama said in Turkey.

"Many other Americans have Muslims in their families or have lived in a Muslim-majority country -- I know, because I am one of them."

Trying to expel the legacy of the often referenced but rarely mentioned former president George W. Bush, Obama said sorry for recent US "arrogance" and "derision" towards European allies.

Obama-mania meanwhile crashed through Britain, France, Germany and the Czech Republic, as the local press gushed over the new president's charisma and his glamorous wife Michelle.

On substantive policy, in a major speech in Prague, Obama heralded a far-reaching bid to abolish nuclear stocks, ban nuclear tests and halt production of fissile material.

He urged the world to unite to stop a terrorist killing hundreds of thousands in "New York, or Moscow, Islamabad or Mumbai, Tokyo or Tel Aviv, Paris or Prague."

The global span of that remark encapsulated Obama's attempt to convince his hosts that Afghan-based terrorists or loose nuclear weapons were as much a threat to them as they were the United States.

In three summits and 14 bilateral meetings in five countries, Obama said he wanted to "listen and learn" -- in another dig at Bush.

And US and foreign officials said Obama had helped to unpick key logjams that threatened to derail the London G20 meeting and NATO talks in Strasbourg.

But did he really make gains that will endure past this week's headlines?

Aides cite progress at the G20 which endorsed a huge raft of new spending and a crackdown on tax havens to battle the economic crisis.

They said Obama was pleased to get another 5,000 troops from US allies for Afghanistan, and won NATO backing for his effort to train the Afghan National Army and police forces.

But critics carped Obama only managed to lure short-term military deployments and did not secure the kind of coordinated global economic stimulus spending for which some had hoped.

Several times, the world's most intractable problems emerged, and suggested they might be immune to the Obama charm.

North Korea's launched a rocket during his trip -- and within days, the US was wrangling with Russia and China on how to respond -- despite Obama's summits with Russian President Dmitry Medvedev and China's Hu Jintao.

Obama forged an almost affectionate relationship with Nicolas Sarkozy but got a lashing from the French President when pushing Turkey's claims for EU membership.

White House aides dismissed the idea that such spats proved little had changed.

"Why didn't the waters part the sunshine and all the ills of the world disappear because President Obama came to Europe this week?" his top political advisor David Axelrod said.

"That will take just a few weeks," he quipped before Obama headed home Tuesday, via Iraq.

One Obama aide said privately that a corresponding European swing in a year's time might be the right time to judge whether Obama's new tone had got results.

Another Obama aide was speaking about the "reset" US relationship with Russia, but may have been mulling Obama's agenda as a whole when he said "to establish an ambitious agenda does not mean we're going to fulfil it.

"We have no illusions about that. We are not being naive about this."

AFP/Expatica