The Taliban and allies such as the al Qaeda network have stepped up raids in the past 18 months in Afghanistan despite the presence of nearly 50,000 foreign troops led by NATO and the US military, as well as some 100,000 Afghan forces.
In that period thousands of people, including more than 200 Western troops, have died in the violence, the bloodiest since US-led forces overthrew the Taliban government in 2001 in retaliation for the Sept. 11 attacks on the United States.
In some NATO countries public opinion is against the presence of their soldiers in Afghanistan.
Talking to reporters after holding talks with visiting Canadian Prime Minister Stephen Harper, Karzai said the world, and in particular the West, needed to stay in Afghanistan to help Afghans, but also for its own security.
''Let us complete the job as hard as it may look at times,'' Karzai commented when a Canadian journalist asked the two leaders about rising opposition among Canadians to having their troops in Afghanistan.
''It is a necessary price that we have to pay; the Afghans are paying that price, the rest of the world is paying that price together with us... and let us complete it and not abandon it half way,'' Karzai said.
He said the world should bring much-needed help for the Afghan people and enable government forces to stand on their own feet to prevent the return of the militants.
''There are still the remnants of terrorism that if we leave half the way, will re-emerge and will haunt you back home whenever they want,'' Karzai said, citing the September 11 attacks.
Harper said Canada's engagement in Afghanistan, its biggest foreign deployment in the world, was the right thing to do.
He said bringing security to Afghanistan could not be achieved through military means alone and added there was need for developing Afghanistan's economy, social and government infrastracture.
REUTERS DS KP1750