STOCKHOLM, Sweden (AP) _ The government Friday introduced a preliminary timetable for phasing out nuclear energy beginning in the mid-1990s.

Energy Minister Birgitta Dahl said the move was likely to push up electric power costs by 50 percent. Sweden has been preparing for the step for several years. The country has 11 nuclear reactors in operation.

''We will carry out a steady, stable and purposeful dismantling of nuclear power and therefore it is neccessary to start as early as possible,'' Energy Minister Birgitta Dahl said in formally presenting the energy bill to Parliament.

The proposal called for the shutdown of two nuclear power plants between 1993 and 1996. It did not specify which ones would be shut down first.

There has been widespread speculation that reactors at Barseback, across the Oresund Strait from Copenhagen, Denmark, and at Ringhals on the west coast, would be among the first to be shut down. Dahl would not comment on that.

The bill did not provide a concrete program for covering the loss of power when the plants are closed. Dahl said however that a prerequisite is that power consumption be reduced to cover about half of the loss. Imports of natural gas, conversion of nuclear plants to oil, and alternative energy sources would make up for the rest. Hydroelectric power is to be expanded by 1,500 megawatt utilizing one of the few remaining northern rivers, Dahl said.