· Findings also show fall in support for war on terror · Decline in America's image 'all to do with Iraq'

George Bush's six years in office have so damaged the image of the US that people worldwide see Washington as a bigger threat to world peace than Tehran, according to a global poll.

The Washington-based Pew Research Centre, in a poll of 17,000 people in 15 countries between March and May, found more people concerned about the US presence in Iraq than about Iran's alleged nuclear weapons ambitions.

The Pew Centre said: "Despite growing concern over Iran's nuclear ambitions, the US presence in Iraq is cited at least as often as Iran - and in many countries much more often - as a danger to world peace."

The survey, carried out annually, shows a continued decline in support for the US since 1999. The US image for most of the 20th century has been relatively positive, being regularly identified with democracy, human rights and openness in spite of criticism from the left, which reached a height during the Vietnam war, and a residual suspicion in the Muslim world.

But even in the UK, Washington's closest ally, favourable ratings have slumped from 83% in 1999 to 56% this year. The pattern is similar in France, down from 62% to 39%, Germany 78% to 37%, and Spain 50% to 23%.

In Muslim countries with which the US has traditionally enjoyed a good relationship, such as Turkey - a member of Nato - and Indonesia, there have also been slumps. In Indonesia favourable ratings for the US have dropped from 75% to 30%, and in Turkey from 52% to 12%.

"It's all [because of] Iraq," Carroll Doherty, associate director of the Pew Centre, said. He added that it was a sign of how "dangerous Iraq is to the US image" that, in spite of common cause between the US and Europeans on Iran, there had been no improvement in the American position in Europe.

Mr Doherty said: "Short-term measures do have an effect. The outpouring of US tsunami aid helped in Indonesia and India but that faded quickly, and now we see US aid for Pakistan earthquake victims only helping at the margins." Favourable ratings of the US in India dropped over the year from 71% to 56%.

He said US domestic polling indicated that Americans were well aware of how the country was perceived abroad. The US image has become a political issue, with Republicans saying it doesn't matter as long as the correct policies are being pursued overseas, while Democrats argue that repairing the country's image and relationships will be a priority for the next president in 2009.

The poll provides little comfort for Condoleezza Rice, who has worked hard at improving relations with Europe since becoming Secretary of State last year.

As part of the overall decline in US support, the survey also records a drop in support for the US-led "war on terror", even in countries such as Spain, in spite of the Madrid bombings two years ago by al-Qaida that left 192 dead. Support for the "war on terror" dropped in Spain from 26% last year to 19% this year.

Throughout the period the poll was conducted the crisis over Iran's nuclear programme, intensified by hardline comments from its president, Mahmoud Ahmadinejad, was repeatedly in the news. Iraq, too, has been in the news on an almost daily basis, with the formation of a new Iraqi government being accompanied by fears of a civil war.

Only in the US and Germany is Iran seen as a greater danger than the US in Iraq. Public opinion in 12 of the other countries - Britain, France, Spain, Russia, Indonesia, Egypt, Jordan, Turkey, Pakistan, Nigeria, India and China - cite the US presence in Iraq as being the greater danger. Opinion in Japan was evenly divided.

As well as Iraq and Iran, the Israeli-Palestinian conflict is also high on the list of issues that present a danger to world peace. Public opinion in about a third of the countries polled put it at the top of their list of threats.

In the UK, the second biggest contributor of troops in Iraq, 60% said the Iraq war had made the world more dangerous. Only 30% said it had made the world safer, and 41% of British people said the US presence in Iraq represented a great danger to world peace, with 34% citing Iran as a big threat.

By contrast, concern about Iran has almost doubled in the US over the past two years. Some 46% of Americans view Mr Ahmadinejad's government as "a great danger" to stability in the Middle East and world peace, up from 26% in 2003. The concern in the US is shared in Germany, where 51% see Iran as a great danger to world peace, against 18% three years ago.