But other researchers said it was still unclear whether recovery would require further reductions in emissions or simply more time, or both.

That would require tax increases or sharper reductions in spending.

California passed a law last year requiring reductions in carbon dioxide for automobiles.

And more important, reducing the trade deficit required solid reductions in the budget deficit.

The proposal for achieving the $57.5 million in cuts seemed itself to require significant reductions.

The plan would require steep reductions in pollution from coal-fired plants over the next 25 years.

Many economists outside the administration predict that the recent tax cuts will eventually have to be reversed or require big reductions in government programs.

A buyer undoubtedly would also require huge reductions in labor costs.

The agency also said it expected to require even sharper reductions in the volatility of gasoline within the next two years.

They added, though, that over time the permit system would allow the federal agency to require reductions in emissions if the air quality remained poor.