We have studied magnetotail reconnection under the influence of a dawn to dusk electric field applied at the high-latitude tail boundary using a two-dimensional resistive MHD code. We found that the basic unstable sequence of tearing and plasmoid formation and ejection was not changed if the external electric field was fairly uniform. The externally forced compression, however, could shorten the onset time and the growth time of the evolution. The faster growth can be understood by the fact that the forced compression gradually alters the lobe field strength and the plasma sheet width and reduce thereby the relevant Alfv¿n time. In fact, if the evolution of the cases with imposed electric field is rescaled on the basis of these characteristics parameters, a good quantitative agreement with the case without external electric field is found.