Peace protesters planning a march to mark the US president's state visit next week say police are planning to seal off large parts of central London.
Protesters want to march through central London
Campaigners are planning a "Stop Bush" protest march through central London on 20 November, but say the Metropolitan Police are trying to block them.
As President Bush and his wife are due to stay at Buckingham Palace, there has been speculation much of the Mall and Whitehall will be closed off along with parts of the City.
Scotland Yard says it is not revealing details of road closures yet for security reasons, but says it will facilitate lawful demonstrations.
But the Stop the War Coalition says it will not accept any route that avoids Parliament.
It follows a row between the Metropolitan Police and civil rights campaigners over the use of anti-terror powers against protesters at an arms fair in September.
Campaign spokesman John Rees told BBC London: "It seems as if they (the police) are going to comply with the White House's request to create an exclusion zone in central London during George Bush's visit.
"And they have told the Stop the War Coalition they won't agree to a route that goes through Parliament Square or Whitehall."
The president's last visit was met with some protest
It will be Mr Bush's first visit to London since July 2001, which was met with some protest but little disruption.
But in the wake of the 11 September terror attacks and large demonstrations in London against the war in Iraq, police are facing a huge security operation.
Jeremy Corbyn, MP for Islington North and a Stop the War activist, told BBC Radio 4's Today programme: "We've had long discussions with the police and one gets the feeling that there is a bigger hand somewhere that is trying to prevent a march going along Whitehall and past Parliament Square.
"The Americans are actually running the security operation in London as well... I'm getting a bit alarmed about the degree of invasion of our capital by the Americans.
"The idea of closing off large parts of London to ensure that President Bush is taken well away from any protests or demonstrators seems a little insensitive and an enormous inconvenience to an awful lot of people."
Metropolitan Police Commissioner Sir John Stevens said: "Because of the security implications we won't be announcing the road closures until the last minute.
"We will keep those to a minimum, we must make sure London continues to operate as normally as possible."
But James Rubin, former US assistant secretary of state during the Clinton presidency, said there were two issues for the White House to consider.
"One is after 9/11 and the possibility of a direct attack on the president and his entourage that has existed in the last couple of years, security caution is very high," he said.
"But there's also something else new in that President Bush is coming to a country that was the scene of enormous demonstrations.
"I think he is coming to a city that will represent extreme opposition in large numbers to what he has tried to do in Iraq."