Federal regulators gave clearance Wednesday for a large and controversial field test of genetically engineered trees planned for seven states stretching from Florida to Texas.

The test is meant to see if the trees, eucalyptuses with a foreign gene meant to help them withstand cold weather, can become a new source of wood for pulp and paper, and for biofuels, in the Southern timber belt. Eucalyptus trees generally cannot now be grown north of Florida because of occasional freezing spells.

The Agriculture Department, in an environmental assessment issued Wednesday, said no environmental problems would be caused by the field trial, which could involve more than 200,000 genetically modified eucalyptus trees on 28 sites covering about 300 acres.

The permit would be issued to ArborGen, a biotechnology company owned by three big forest products companies: International Paper and MeadWestvaco of the United States, and Rubicon of New Zealand.