Updated

HAVANA -- The government of Cuba is facing a midnight deadline to release the last of 52 political prisoners.

So far, Cuba has released 39 prisoners of conscience that it agreed last July to let go. The prisoners were exiled to Spain, accompanied by their families. Thirteen remain in prison.

But those 13 prisoners have refused to leave the island, directly challenging the Havana government. Some say they will continue their fight for democratic political change the moment they leave jail.

As the hours tick down, a confrontation appears to be looming.

The wives and mothers of the remaining prisoners marched through Havana on Sunday. They say if the government fails to honor the agreement, the government can expect protests and international condemnation.

Cuban officials have declined to comment on the deadline.