Web services technology is vulnerable to security threats similar to other technologies which are based on communication over internet. Some applications working over internet typically require strong authentication. The security requirements of a scenario may involve interdomain authentication mechanisms. These domains may be operating using different technologies. In order to enable such scenarios, we leverage existing approaches with emerging standards and propose an architecture. Our proposed architecture takes advantage of XML technology and emerging SAML standard. The most important aim of the proposed architecture is platform indepedence. Our proposed architecture includes a Security Token Service and a protocol for communication between token requesters, consumers and issuers. Although, the exact flow of execution depends on the scenario, we believe our approaches can be used as common ground for implementation.