SINGAPORE, May 17 (Reuters) - Indonesian ride-hailing and payments firm Gojek and e-commerce leader Tokopedia announced a merger on Monday in a transaction that would create a technology powerhouse in the country’s largest deal. Sources familiar with the situation had earlier said the companies were seeking a $18 billion merger. Neither firm confirmed a valuation for the merged group. Alibaba Group Holding and SoftBank Group Corp are among Tokopedia’s investors, while Gojek’s include Warburg Pincus and Tencent Holdings. (Reporting by Anshuman Daga: Editing by Neil Fullick and Kenneth Maxwell) Our Standards: The Thomson Reuters Trust Principles.