US Defense Secretary Robert Gates is in the south of Afghanistan after touching down on Friday.

Mr Gates is in the country to meet battle-line US soldiers, who have been described as the spear-tip troops in the Taliban’s Afghan heartland.

He arrived in Kabul on Thursday on an unannounced trip after attending ceremonies in Iraq to mark the formal end to US combat engagement there after seven years.

In Kabul, at a joint news conference with President Hamid Karzai, he said that the surge of 30,000 additional troops ordered by President Barack Obama was nearly complete.

The extra deployment will strengthen the international force to 150,000.

After Kabul, his first assignment Friday was to go to a small NATO base outside Kandahar city.

Kandahar, one of the hottest spots in the intensifying war against the insurgents, was the scene this week of a battle in which eight soldiers were lost to insurgent violence.

Mr Gates said to the troops: "You all are clearly on the frontline. This has been a very tough week for you all. What makes a difference in this whole campaign is your success here in Kandahar city."

326 Americans have been killed this year in Afghanistan.