Malaysian Prime Minister Najib Razak called Monday for closer economic integration in East Asia to combat future crises. Najib said the current global downturn and the 1997-98 regional crisis had shown that 'deepening East Asian economic and financial cooperation are no longer an option but an imperative.' The Malaysian leader was speaking at a business forum, before the start of a summit between South Korea and the 10-member Association of Southeast Asian Nations. South Korea and ASEAN will Tuesday sign an investment accord, the last step in a full free trade deal. Najib praised the conclusion of 'challenging negotiations' between ASEAN members and South Korea, the continent's fourth largest economy. 'This signifies the commitment by ASEAN and Korea to take our relationship to a higher plane through further integration of our economies,' he said. Najib said lessons learnt from the current crisis can contribute to a strong and dynamic East Asian region which would act as a catalyst for global growth. 'We have to strengthen the economic resilience of East Asia,' he said. 