  We present an analysis of the XMM-Newton observation of the symbiotic star AG
Peg, obtained after the end of its 2015 outburst. The X-ray emission of AG Peg
is soft and of thermal origin. AG Peg is an X-ray source of class beta of the
X-ray sources amongst the symbiotic stars, whose X-ray spectrum is well matched
by a two-temperature optically-thin plasma emission (kT_1 ~ 0.14 keV and kT_2 ~
0.66 keV). The X-ray emission of the class beta sources is believed to
originate from colliding stellar winds (CSW) in binary system. If we adopt the
CSW picture, the theoretical CSW spectra match well the observed properties of
the XMM-Newton spectra of AG Peg. However, we need a solid evidence that a
massive-enough hot-star wind is present in the post-outburst state of AG Peg to
proof the validity of the CSW picture for this symbiotic binary. No short-term
X-ray variability is detected while the UV emission of AG Peg shows stochastic
variability (flickering) on time-scales of minutes and hours.
