Israeli Prime Minister Menachem Begin today he has reached agreement with Maj. Saad Haddad, commander of the southern Lebanese Christian militias, on the conduct of the militias toward the U.N. peacekeeping force in Lebanon.

Begin also said Haddad had agreed to try to avoid hitting civilian populations in southern Lebanon when his artillery is shelling Palestinian guerrilla positions.

After a meeting following Haddad's release from a Haifa hospital, where the militia leader was treated for exhaustion, Begin said, "It was agreed between us -- and I want to stress the words 'agreed between us' -- that there won't be any clashes with the international peacekeeping force and that permanent efforts will be made to avoid any attempts to hurt the civilian population."

Haddad's forces, which are supported by Israel, have been repeatedly criticized by the United Nations and the United States for attacking U.N. positions in the buffer zone north of the Christian enclave and for shelling densely populated civilian centers. Tyre and Nabatiya, Palestinian-controlled cities, are favorite targets of the militia gunners and artillery units of the Israeli Army as well.

Begin's account of his and Haddad's agreement was carefully phrased, since Israel's position has always been that it supports Haddad, but has no control over his actions.