Guyana warned Monday it would "vigorously" resist any attempt by Venezuela to enforce a new claim over coastal waters where Exxon Mobil recently announced an important oil find. Caracas issued a decree May 27 laying claim to waters off the Essequibo, a disputed territory that borders Venezuela and encompasses more than half of Guyana. The Venezuelan action came less than a month after Exxon Mobil said it had made a "significant" discovery in an offshore concession granted by Guyana.