  We discuss thermodynamic properties of open confining strings introduced via
static sources in the vacuum of Yang-Mills theory. We derive new sum rules for
the chromoelectric and chromomagnetic condensates and use them to show that the
presence of the confining string lowers the gluonic pressure in the bulk of the
system. The pressure deficit of the gluon plasma is related to the potential
energy in the system of heavy quarks and anti-quarks in the plasma.
