  We propose a scheme for tunable coupling of phase-coupled flux qubits. The
phase-coupling scheme can provide a strong coupling strength of the order of
Josephson coupling energy of Josephson junctions in the connecting loop, while
the previously studied inductive coupling scheme cannot provide due to small
mutual inductance and induced currents. We show that, in order to control the
coupling, we need {\it two} dc-SQUID's in the connecting loop and the control
fluxes threading the dc-SQUID's must be in {\it opposite} directions. The
coupling strength is analytically calculated as a function of the control flux
at the co-resonance point.
