The foreign secretary is visiting British forces HQ in Iraq

Flying in to the Iraqi capital Baghdad Mr Straw said the incidents had increased London and Washington's determination to root out remnants of Saddam Hussein's regime.

That pledge was reinforced by US President George W Bush, who on Tuesday talked of the massive and long-term undertaking by coalition troops that would be necessary.

There is absolutely no question of those attacks leading to a pull-out Jack Straw Foreign Secretary

Mr Straw told BBC News he hoped a council of Iraqis to draft the country's new constitution could be set up by the middle of next month.

The minister, the most senior British politician to visit Baghdad since Saddam Hussein's regime's demise in April, is in Iraq to assess the security situation since the death of the six Royal Military Police on 24 June.

The bodies of the men, who were killed at a civilian police station in Al Majar al-Kabir in the south of the country, were being returned to RAF Brize Norton in Oxfordshire for a repatriation ceremony on Tuesday.

He said he believed the incident was "relatively isolated", although it was "extremely concerning".

Promise

Mr Straw said British forces would always remember the pledge to find the killers, adding: "We are not going to forget."

The circumstances of their deaths are still being investigated by the Ministry of Defence.

Mr Straw, who flew into Baghdad International Airport amid tight security, was taken into the city in a fleet of US Black Hawk helicopters as the route was considered too dangerous to travel by car.

Bush: We will stay on the offensive

Earlier, he visited the headquarters of the British forces in Iraq in Basra to discuss the security situation with their commander, Major General Sir Peter Wall.

Mr Straw met members of the Royal Military Police and expressed "deep shock" at the deaths of their colleagues.

He told reporters: "We will be staying in Iraq for as long as it takes to support the Iraqi people, to establish representative government and to establish decent social and economic services for the Iraqi people.

"There is absolutely no question of those attacks leading to a pull-out."

He added: "People are making a terrible mistake if they think we are going to run away from this - that is not the way the British forces operate.

"We have a responsibility in any event to secure this country."

Iraqi police

Mr Straw said while the security situation was better than it was two months ago, there were still elements of the Baath Party and the Fedayeen "operating in a relatively organised way" against coalition forces.

He said General Wall had not made any request for reinforcements, although it was understood that the option of sending more troops remains under review.

During his visit Mr Straw told a class of 30 Iraqi police recruits: "I know that Baghdad isn't London or New York, but bad people are bad people and the lessons of our policing are ones that can be transferred."

Long-term commitment

Mr Straw told BBC Radio 4's World At One: "It looks as though one can be relatively optimistic about a governing council, the interim authority... probably getting under way by the middle of this month...

"Everybody recognises that the quicker we get Iraqis in place running Iraqi governing institutions and with a calendar leading to much more representative government, the better it is for everybody."

Iraq's most senior Shia cleric has issued a fatwa calling for elections to choose Iraq representatives.

Elections were not possible without a constitution, said Mr Straw, but he hoped the council could be established with an element of consent from Iraqis.

At a military swearing-in ceremony on Tuesday, Mr Bush also talked of the massive and long-term undertaking that would be necessary.