unite nations u.n. secretary-general antonio guterres say friday serious concern escalate tensions saudi arabia lebanon essential avert new conflict region indeed worry hope see escalation unite nations chief tell reporters essential new conflict erupt region could devastate consequences guterres say intense contact yesterday saudi arabia lebanon countries region comment come amid deepen crisis two middle eastern nations thrust tiny lebanon saudi arabia region powerhouse iran early week saudi arabia accuse lebanon declare war cite aggression iran-backed lebanese shi ite group hezbollah friday hezbollah leader sayyed hassan nasrallah accuse saudi arabia declare war lebanon hezbollah midst conflict saad al-hariri lebanon former prime minister unexpectedly resign post weekend lebanese authorities say hold saudi arabia charge riyadh deny unite nations chief 'very worry saudi-lebanon tensions