MOROCCANS PLAN MARCH IN SAHARA
Moroccan King Hassan II announces that he soon will lead march of 350,000 unarmed Moroccans into Spanish Sahara to claim territory for Morocco, broadcast; announcement follows declaration by Internatl Ct of Justice that it cannot 'establish any tie of territorial sovereignty' over Spanish Sahara either for Morocco or Mauritania; Hassan warns Algerian Govt, which has refused to back Morocco's claims to Sahara, that it should not interfere; proposal for referendum is believed to have backing of majority in UN; march appears to be way of heading off such vote, which Moroccans feel will go against them; map (M)