Testing the relativistic effect of the propagation of gravity by very longbaseline interferometry

It is shown that the finite speed of gravity affects very long baseline int erferometric observations of quasars during the time of their line-of-sight close angular encounter with Jupiter. The next such event will take place in 2002 September 8. The present Letter suggests a new experimental test of general relativity in which the effect of the propagation of gravity can b e directly measured by very long baseline interferometry as an excess time delay in addition to the logarithmic Shapiro time delay.