We report the discovery of a systematic constant time lag between the X-ray and radio flares of the gamma-ray binary LSI +61 303 , persistent over long , multi-year , time scale .
Using the data of monitoring of the system by RXTE we show that the orbital phase of X-ray flares from the source varies from \phi _ { X } \simeq 0.35 to \phi _ { X } \simeq 0.75 on the superorbital 4.6 yr time scale .
Simultaneous radio observations show that periodic radio flares always lag the X-ray flare by \Delta \phi _ { X - R } \simeq 0.2 .
We propose that the constant phase lag corresponds to the time of flight of the high-energy particle filled plasma blobs from inside the binary to the radio emission region at the distance \sim 10 times the binary separation distance .
We put forward a hypothesis that the X-ray bursts correspond to the moments of formation of plasma blobs inside the binary system .