Protesters scuffled with riot police in central London Sunday as US President George W. Bush held talks with British Prime Minister Gordon Brown, nearly at the end of a farewell European tour.

Iran and Iraq were expected to on the menu over dinner in Downing Street, whilst the two men meet for more formal talks on Monday, before Bush heads for Northern Ireland and then home.

Bush will also have breakfast with Brown’s predecessor Tony Blair, whose support for the US President’s 2003 invasion of Iraq triggered worldwide protests and prolonged diplomatic rifts.

Protests have been rare during Bush’s week-long tour of Europe, which has taken him to Slovenia, Germany, Italy, the Vatican City and France.

But scuffles broke out after protestors tried to breach police lines sealing off Whitehall, the main government thoroughfare in the heart of London where the two leaders were meeting.

Some 13 people were arrested in the ensuing violence, Scotland Yard, although the situation returned to a tense calm before the end of the Downing Street evening meeting.

Bush had started his visit by taking afternoon tea with Queen Elizabeth II in Windsor, before heading in to central London to meet Brown.

But even before Bush’s presidential Air Force One airplane touched down at London Heathrow, top officials had to dismiss a newspaper report suggesting he would warn Brown against a premature withdrawal from Iraq.

"There is no disagreement between us, between the President and Prime Minister Brown, on this issue, period," US National Security Adviser Stephen Hadley told reporters.

Another US official branded the report in the Observer newspaper "ludicrous", and a Downing Street spokeswoman told AFP that there was "absolutely no disagreement" with the United States over the issue.

Hadley said the talks would focus on tightening sanctions on Iran over its refusal to freeze its suspect nuclear programme, a subject that Bush said on Saturday had dominated his European tour thus far.

"That (sanctions) seems to be pretty clear commitment and consensus throughout Europe," the adviser said.

Both sides said the talks would also include climate change, the state of the global economy and ongoing efforts to clinch an international trade liberalisation deal.

Since Bush’s visit to Paris, commentators have made much of the new warmth in ties with France, and what are seen to be the cooler relations between Bush and Brown, at least compared to the British PM’s predecessor Blair.

But US aides were at pains to underline the enduring close ties between Britain and the United States.

"Brown is a different personality than Blair. The president, I think, has forged a good, close relationship with each and both of them," said Hadley.

But he insisted: "What underlines that relationship is the fact that the United States and Britain continue to have a very special relationship."

Blair, who is now the envoy for the Middle East Quartet, is due to have breakfast with Bush on Monday morning, shortly before Bush’s formal talks with Brown.

"Obviously it’s going to focus principally on the Middle East peace process and Mr. Blair’s work there," said Blair’s spokesman Matthew Doyle.

Bush’s last visit to London, in November 2003, saw three full days of protests, with tens of thousands of people marching past Downing Street marshalled by 5,000 police officers.

Brown went to the US presidential retreat at Camp David outside Washington last July, soon after taking over from Blair, to reaffirm transatlantic ties. He also visited the White House in April this year.