De Hoop Scheffer is in Afghanistan to review the 26-nation alliance's expansion into the volatile southern part of the country, which has recently seen an upsurge in fighting between coalition forces and Taliban as NATO tries to take control of the region.
NATO nations are expected to give their final go-ahead to expand their mission July 26 at NATO headquarters in Brussels.
The NATO chief, who was joined on his trip by NATO's supreme military commander, U.S. Gen. James L. Jones, will meet Afghan President Hamid Karzai later Thursday and his defense and interior ministers, according to the AP.
NATO is currently deploying around 8,000 mostly British, Canadian and Dutch troops to the south, taking the ISAF mission to about 18,000 by September.
Canadian troops in Kandahar and British forces in Helmand, currently working with U.S. troops as part of an anti-terror campaign, have met stiff resistance in outlying areas from insurgents wanting to disrupt their mission there.
The NATO alliance hopes eventually to take on eastern Afghanistan by November, completing its expansion across the country and increasing its total numbers to 21,000.
The United States has at least 21,000 troops in Afghanistan, but there has been talk of a cut of up to 20 percent. Many of those that remain will be incorporated into the NATO force. However, the U.S. will also maintain a combat force independent of NATO to hunt down Taliban and al-Qaida militants.