By BEN LEFEBVRE And CASSANDRA SWEET

Cheniere Energy Inc. received federal approval Monday to construct what would be the first major natural gas export facility in the lower 48 U.S. states, putting the company a step closer to shipping some of America's newly abundant natural gas abroad.

The Federal Energy Regulatory Commission gave its approval for the construction of a liquefied natural gas export facility in Cameron Parish, La., clearing the final regulatory hurdle for Cheniere. Pending financing for the project, estimated to cost $10 billion, Cheniere would become the only large-scale LNG exporter in the U.S.

"This was clearly a big step," said Cheniere spokesman Andrew Ware. "It's a milestone." Shares of Cheniere were up 6.5% at $18.10 in after-hours trading.

The commission approved construction of the facility and authorized Cheniere to export gas for 20 years. Cheniere has already lined up supply contracts with Britain's BG Group PLC, Gas Natural Fenosa, Gail (India) Ltd. and Korea Gas Corp.

A technology-driven boom in U.S. natural gas production has depressed prices to around $2 per million British thermal units. That has attracted the attention of customers in other countries—particularly in Asia—where the commodity can cost nearly 10 times as much.

Several other companies have applied to export natural gas from U.S. facilities, although Cheniere's plans are the furthest along.

Opponents of U.S. LNG exports have warned that shipping U.S. natural gas overseas could cause domestic gas prices to rise. Rep. Edward Markey (D., Mass.) said Monday that exports would boost costs for makers of steel, plastics and fertilizers, and he predicted that export approvals would result in "exporting our manufacturing jobs abroad along with the fuel."

The Department of Energy is expected to release a report on the possible economic effects on LNG exports late this year.

Cheniere still must find about $4 billion in financing to build and develop the export facility, which it hopes to do within six months. The company on Monday said it was working with eight banks to arrange the necessary financing. Cheniere in February secured $2 billion for the project from Blackstone Group LP.

The Louisiana facility was originally designed to import natural gas, when it seemed that the U.S. couldn't fill its needs from domestic supply. Houston-based Cheniere fell deeply into debt in the late 2000s after the U.S. natural-gas production boom made imports unnecessary.

Cheniere's facility, called Sabine Pass, would have the capacity to export up to 2.2 billion cubic feet, or 16 million tons, of natural gas a year, according to FERC. Cheniere hopes to start LNG exports by 2015.

Write to Ben Lefebvre at ben.lefebvre@dowjones.com and Cassandra Sweet at cassandra.sweet@dowjones.com