Tony Blair has promised British troops serving in southern Afghanistan they will be given whatever resources they require to achieve a successful outcome.
The Prime Minister also hit out at "negative" media reporting of the mission.
Mr Blair, in an interview with the Armed Forces broadcaster BFBS, acknowledged that the fighting in Helmand province had been "very, very tough".
But he insisted the mission by British and other Nato forces was vital to prevent the country falling back into the hands of al Qaida and the Taliban, and again becoming a training ground for terrorists.
Since the start of operations in Afghanistan in November 2001, 40 British forces personnel have died.
Of these, 18 were killed in action, while 22 are known to have died either as a result of illness, non-combat injuries or accidents.
Since May, an average of five soldiers a week have been killed out of the 18,500 serving with Nato's International Security Assistance Force (Isaf).
Mr Blair said it was essential to keep on explaining the importance of what the troops were doing in the light of the "negativity" of the reporting in some parts of the media.
And he reaffirmed his commitment to provide any additional resources requested by commanders on the ground.
"If the commanders on the ground want more equipment, armoured vehicles for example, more helicopters, that will be provided. Whatever package they want we will do," he said.
