The U.S. Commercial Service
If you are a U.S. company that is interested in doing business in Greece, or a Greek company that is interested in sourcing U.S. products or services, your first stop should be the U.S. Commercial Service's BuyUSA web site for Greece. The page is available in English or Greek.
Note: If you are a Greek company that is interested in providing primarily defense-related technologies, products, or services to the United States, your first stop should be getting in contact with the U.S. Office of Defense Cooperation’s Defense Cooperation in Armaments program manager to discuss your ideas.