  The extended X-ray emission observed at arcsec scales along the propagation
trajectory of the precessing relativistic jets of the Galactic microquasar SS
433 features a broad emission line, with the position of the centroid being
significantly different for the approaching and receding jets ($ \approx7.3 $
and $ \approx6.4 $ keV, respectively). These observed line positions are at
odds with the predictions of the kinematic model for any of the plausible
bright spectral lines in this band, raising the question of their
identification. Here we address this issue by taking into account time delays
of the emission coming from the receding regions of the jets relative to that
from the approaching ones, which cause a substantial phase shift and distortion
of the predicted line positions for the extended ($ \sim 10^{17}$ cm) emission
compared to the X-ray and optical lines observed from the central source
(emitted at distances $ \sim 10^{11}$ cm and $ \sim 10^{15}$ cm, respectively).
We demonstrate that the observed line positions are fully consistent with the
Fe XXVI Ly$\alpha$ ($E_0=6.96$ keV) line emerging from a region of size $
\sim6\times10^{16}$ cm along the jet. This supports the idea that intensive
reheating of the jets up to temperatures $ \gtrsim10 $ keV takes place at these
distances, probably as a result of partial deceleration of the jets due to
interaction with the surrounding medium, which might cause collisions between
discrete dense blobs inside the jets.
