Britain will deploy up to 5,700 troops in Afghanistan during the coming months to support an expanded NATO mission into a dangerous southern region.
Defense Secretary John Reid has announced the increase in British forces in a speech to the House of Commons.
He acknowledges the mission will be dangerous, but he says it is a risk that must be taken.
"Whatever the difficulties and the dangers, and I do not hide them from the House or from the country, those risks are as nothing compared to the dangers to our country and our people of allowing Afghanistan to fall back into the clutches of the Taleban and international terrorism," he said.
Mr. Reid says Britain will contribute most of its new troops to a 3,300-man, Canadian-led NATO mission to southwestern Helmand province, a stronghold of Afghan heroin traffickers.
He says the British contingent in Afghanistan will peak later this year at 5,700 soldiers, then drop as 1,000 military engineers withdraw after they build a base camp.
The deployment represents a sizable growth from the 1,000 British troops currently on duty in Afghanistan.
Meanwhile, the Netherlands is considering whether to send 1,200 troops to join NATO's Afghanistan mission. The Dutch parliament is due to take up the issue next week.
In Brussels, a NATO spokesman says the effort to expand the International Security Assistance Force in Afghanistan from 9,000 to 15,000 troops may be delayed by several months to the latter half of this year.
The United States intends to reduce its troop strength in Afghanistan from 19,000 to 16,500, as NATO takes on more security duties.