The web of Soviet mines in Afghanistan represents a major obstacle to safe resettlement by the more than three million Afghan refugees living in makeshift camps along the Pakistan border. And the mines are a key reason more refugees have not gone back, even though the guerrillas now control virtually all of the countryside. The Soviet-backed Afghan forces still hold the major cities.

To combat the mine threat, the United States, France and Turkey have sent about 65 experts to set up mine-awareness and mine-removal programs for the Afghan refugees, working under the auspices of the United Nations. That education effort began two weeks ago, and it is already evident that far more needs to be done, relief groups say.

''The problem is huge and the program is tiny so far,'' said A. Zahir Mohyuddin, a senior staff member of the Agency Coordinating Body for Afghan Relief.

The use of mining warfare is nothing new. But military analysts say the Soviet mining campaign was extraordinary by any standard. Western estimates of the number of mines strewn across Afghanistan, a nation about the size of Texas, are at best educated guesses. The United States Defense Department puts the number at 10 million to 30 million mines, coming in nearly 30 varieties aimed at people and at vehicles. Scattered by Helicopter

''Most of the mines are antipersonnel devices that have been scattered almost indiscriminately,'' Edward W. Gnehm Jr., a Defense Department deputy assistant secretary, said in testimony before the House Foreign Affairs Subcommittee on Asian and Pacific Affairs last week.