LONDON -- US President George W. Bush was greeted with noisy protests Sunday as he headed for talks with British Prime Minister Gordon Brown notably on Iran, while both sides vigorously denied any rift over Iraq.

The president's London visit was the penultimate stop on his European farewell tour before leaving office. It is the first time Brown, who took over from Bush's close political ally Tony Blair, has hosted him on home soil.

Bush was also due to meet Blair during the London stopover, a spokesman for the former premier and now Mid-east envoy said.

Some 400 campaigners opposed to British and US involvement in Iraq and Afghanistan gathered near Downing Street even before Bush arrived for an evening dinner with Brown, police said.

"George Bush: terrorist," shouted the protestors, gathered peacefully in Parliament Square, and watched over by some 1,200 police including armed officers prepared for "all outcomes," said a Scotland Yard spokeswoman.

Protests have been a rare sight during Bush's week-long tour of Europe, which has taken him to Slovenia, Germany, Italy and France.

Bush, flying in from Paris, started his visit with afternoon tea with Queen Elizabeth II before the Downing Street dinner with Brown, and more talks Monday. He will head to Northern Ireland on Monday, his last stop before flying home.

Even before Bush's presidential Air Force One airplane touched down at London Heathrow, top officials dismissed a report in The Observer newspaper that suggested 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.

The two agree that any withdrawal "has to be a result of progress on the ground, on the advice of our military, and not according to any arbitrary schedule," said Hadley.

Another US official branded the report "ludicrous." 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 program -- a subject 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 liberalization deal.

Commentators have made much during Bush's trip of the new warmth in ties with France, and the perceived cooler relations between Bush and Brown, compared to the British PM's predecessor Blair.

US aides stress the "special relationship" 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 his 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 marshaled 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.