The plant is to be built in a buffer zone next to the Paracas National Reserve, where a number of fishmeal plants are also located.

"It (the consortium) cannot execute any activity referring to the project's off-shore component until it receives a favorable opinion from INRENA (National Institute of Natural Resources) and the definitive approval of the EIA (Environmental Impact Study)," Bonelli told foreign journalists at a meeting late Thursday.

Bonelli also said the consortium must assure protection of the marine ecosystem of the Bay of Paracas, site of the 900,000-acre (375,000-hectare) reserve, by using the best technology during the installation of underground pipes.

Refrigerated butane, propane, naphtha and other fuels will move from the plant via two-mile-long (three-kilometer) pipelines to ships for export.

The consortium must also create an environmental guarantee "through an environmental insurance policy or another financial instrument," Bonelli said.

A number of other documents, including an updated map of the project's area of influence, a study of currents and waves and a contingency plan must also be presented.

Once these and other measures detailed in a ministerial resolution are taken, the ministry will approve or disapprove the EIA for the plant, he said.

In the meantime the consortium can carry out the on-shore preparatory work for the plant, he said.

Bonelli said, however, that the group is taking a risk by starting construction of the plant prior to the approval of the environmental study.

"Pluspetrol is conscious of the efforts it has to make to hand a sufficient level of information to assure the bay is adequately protected," he said.

Carlos Chirinos of the Peruvian Society of Environmental Law (SPDA) said the main concern of the SPDA and other environmental groups is the technology to be used.

"There is no legal impediment against carrying out this type of activity but the consortium has to assure that it will not affect protected areas.

"It is a problem of costs," Chirinos told Reuters. "If the cost of employing the most adequate technology is too high, this could cause a problem for the project's viability."

Camisea, located in pristine jungle 750 miles (1,200 km) southeast of Lima, has proven reserves of 13 trillion cubic feet of gas and 600 million barrels of gas liquids.

The project, which will pump the gas through a pipeline across the Andes, has faced strong opposition from environmental groups, which have complicated efforts of the companies and the government to obtain the needed financing for the project.

Energy and Mines Minister Jaime Quijandria Thursday said that the Inter-American Development Bank and and the government were working to resolve environmental concerns that have held up approval of a $75 million loan for the project.