Rican territory on a border post of the Sandinist People's Army, using a variety of wns, as well as mortars and 57 mm cannon. I wish to point out that the introduction and use of this latter type of weapon represents a qualitative escalation in the aqqression suffered by my country, which coincides with the disbursement of the misnamed "humanitarian assistance" provided by the United States Government to the forces which are operatinq under its command and are quartereci in Costa Rican territory. I should also like to alert you to the dangerous movement of mercenary forces numberinq approximately 250 armed men in the "El Papatocuaro" sector and of a further qroup of 200 armed men in the Pocosol sector, both of them in Costa Rican territory. The Government of Nicaraqua, through me, urqes the Costa Rican authorities and the Governments of the Contadora Group to take immediate steps, in view of the danqers of the above facts, to prevent and deter further acts of aggression against the people and territory of Nicaragua , acts which obviously obstruct the neqotiations currently qoinq OLI in Panama and which, if they were to continue to go unpunished, would seriously undermine the credibility of the much advertised peace-lavinq attitude and neutrality of the distinguished Government of Costa Rica. Miguel D'ESCOTO BRCCKMANN Minister for Foreign Affairs 