  The sources of ultra-high-energy cosmic rays ($E\gtrsim10^{19}$ eV) is still
an open question in astroparticle physics and in the last years some efforts
were made to understand its origin. In this work we consider white dwarf
pulsars (WDPs) as possible sources of these ultra energetic particles. If some
Soft Gamma Repeaters (SGRs) and Anomalous X-ray Pulsars (AXPs) are considered
as white dwarf pulsars, these sources can achieve large electromagnetic
potentials on its surface and possibly accelerate particle almost of speed of
light and with energies $E \sim 10^{20-21}$ eV. We show that the new scale of
star surface magnetic field and size of SGRs/AXPs as very magnetized white
dwarfs are well described in the Hillas diagram together with the AR Sorpii and
AE Aquarii white dwarf pulsars recently found. SGRs/AXPs described as magnetars
are much above the Hillas line and out of it is expected for normal neutron
star pulsars.
