These factors include statutory requirements, public demands and economic and technological feasibility of efforts to deal with the problems.

Earlier on Tuesday, Mr. Fleischer said the president had doubts about the technological feasibility of such a system.

Moreover, most French security experts doubted the technological feasibility of ballistic missile defense.

Instead of clear and steady progress toward establishing its technological feasibility, the program's managers seem to shift emphasis every few months from one vaunted breakthrough to another.

The emission standards were set without regard to the constraints of technological or economic feasibility that had previously influenced policy-making.

The General Motors Corporation also served notice that it had doubts about the technological feasibility of the longer-range requirements.

Budgetary pressures have forced delays in "Star Wars" research, and major questions remain about the technological feasibility of a space-based defense.

Those laws, like many environmental statutes, call for anti-pollution rules to be based mainly on considerations of public health and technological feasibility rather than cost.

The other criteria are the cost and the technological feasibility.

Although the president spoke of "promising options," there are many questions about technological feasibility.