  We analysed {\it Rossi X-ray Timing Explorer} (RXTE) data of the low-mass
X-ray binary and atoll source 4U 1608-52 obtained on March 3, 1996 in which the
source simultaneously showed a strong single kilohertz quasi-periodic
oscillation (QPO) around 840 Hz, and a 7.5 mHz QPO detected at energies below 5
keV. We find that the frequency of the kHz QPO is approximately anti-correlated
with the 2--5 keV X-ray count rate associated with the mHz QPO. The average kHz
QPO frequency varies by about 0.6 Hz (0.07%) during a mHz QPO cycle over which
the average 2--5 keV count rate varies by about 60 c/s (4%). This is opposite
to the frequency-count rate correlation observed in the same data on longer
time scales and hence constitutes the first example of a sign reversal in the
frequency-flux correlation related to the origin of the flux. Such a sign
reversal is predicted by the radiative disk truncation model for the case where
the flux variations originate on the neutron star but are not due to disk
accretion rate fluctuations. The results support the nuclear burning
interpretation of the mHz QPO, and the interpretation of the kHz QPO frequency
as an indicator of the orbital frequency at the inner edge of the accretion
disk. The varying radiative stresses on the inner disk exerted by the flux due
to the quasi-periodic nuclear burning lead to changes in the inner disk radius
and hence to the observed anti-correlation between kHz QPO frequency and X-ray
count rate. There is a time lag of about ten seconds of the X-ray count rate
relative to the kHz QPO frequency in terms of the anti-correlation we found
between these two quantities, which could be caused by the propagation of the
nuclear burning front on the neutron star away from the equatorial region.
