ALBUQUERQUE -- In a defeat for environmentalists, a federal judge ruled Wednesday in favor of a Bureau of Land Management plan for opening parts of southeastern New Mexico's Otero Mesa to oil and gas drilling.

Critics of the BLM plan, including a coalition of environmental groups and New Mexico state leaders, had claimed the agency failed to properly evaluate whether building roads, pipelines, well pads and other structures would damage the area's ecosystem, which includes North America's largest remaining pieces of Chihuahuan desert grassland.

But in his 43-page ruling, U.S. District Judge Bruce D. Black said the BLM adhered to federal statutes and administrative practices in crafting its plan.

BLM's state director, Linda Rundell, said she was "gratified and encouraged'' by the ruling. "The judge clearly agreed with the analysis that was done and the process that we used,'' Rundell said.

During months of legal wrangling, BLM officials argued that the agency went to great lengths to ensure protecting the ecosystem while serving the needs of land-use parties. Out of the 2 million acres, a total of 1,589 acres would be disturbed by drilling practices such as additional roads, well pads and pipelines, the agency said.

Critics have called BLM's plan vague and claimed it didn't adequately address the impact of drilling on natural resources and wildlife.

Nathan Newcomer, media director for the New Mexico Wilderness Alliance, said Wednesday that the court's decision, while not entirely surprising, put a higher value on drilling for oil and gas than "protecting wild public lands and fresh water aquifers.''

"The court seemed content to listen to an agency whose track record on the environment has been abysmal and put its faith in speculative promises in what may occur rather than the reality of what will occur,'' he said.

Newcomer said the next step would be an appeal to the 10th Circuit Court of Appeals and a renewed effort to get federal legislation passed that would offer permanent protection to the area.

In a statement, Gov. Bill Richardson, said: "Make no mistake; we will continue to fight to protect Otero Mesa.''

Before proceeding, though, he said he would confer with Attorney General Patricia Madrid on whether to continue to challenge the BLM in court or "to fight to protect Otero Mesa through other avenues.''

He also said Black's ruling included a bright spot in that the judge demanded that ŒŒsite-specific'' environmental analyses need to be conducted before any leases are issued.