During the past few years, Grid Computing has matured in terms of programming models and available tools. Some tools like the Globus Toolkit version 2 (GT2) are used in many international high performance distributed computing projects. Recently, the OGSA standard (Open Grid Services Architecture) has been defined, proposing a radically new philosophy compared to that of GT2. Analyzing the evolution of the scientific community working on Grid Computing, we foresee a progressive shift of current developments to this new standard, that already has a reference implementation: GT3. This paper describes the analysis and design of an architecture of OGSA Grid Services that aims to integrate both platforms seamlessly, allowing remote job invocation from GT3 to GT2 holding all the security properties, and transparent for the user.