KANSAS CITY, Mo. - U.S. natural gas supplies have surged dramatically, giving the country a chance to move toward greater energy independence, gas proponents say.

But plans are brewing to start selling some of that gas overseas. Critics say that move would most likely boost gas prices, hurting home­owners in the Midwest, which relies heavily on the fuel for heating.

Higher prices also would be felt by the many industries that rely heavily on gas, and by utilities that are increasingly using gas to generate electricity.

Other critics say it would be a shame to squander the chance to decrease reliance on foreign energy.

The U.S. natural gas outlook has shifted radically in just five years. In 2006, U.S. gas fields were in decline, and the Energy Information Administration expected the U.S. to have to buy a lot of gas from other countries.

But now, with huge amounts of natural gas potentially available in shale formations, the U.S. could have enough to meet its current demand for more than 100 years. The energy agency raised its reserve estimate for shale gas a year ago and then recently doubled it.

By one estimate, U.S. gas reserves now are equal in energy value to Saudi Arabia's oil reserves.

The ample gas supplies also have pushed prices down. U.S. consumers pay half the going wholesale rate in many other developed countries.

But that has made producers consider exporting natural gas to get the higher prices overseas. A Houston company, Chenier Energy Partners, recently agreed to provide natural gas to Gas Natural Fenosa, the largest gas and electric company in Spain and Latin America. The exports could begin in 2015.

"We believe current market fundamentals have created an opportunity for the U.S. to offer natural gas to global markets at competitive prices," Charif Souki, the company's chairman and chief executive, said in a statement.

Natural gas is harder to ship overseas than oil because it has to be supercooled to turn it into a liquid. That's reversed at its destination plant, and then the gas can be put into a country's pipeline system.

Eight U.S. liquefied natural gas plants set up in anticipation of greater gas imports have been underused, and Chenier plans to refit one of them in Louisiana to use for its exports.

The natural gas supply picture changed with the potential of shale gas, which is being tapped with horizontal drilling methods and the improved use of water and chemicals to break up and recover gas in huge underground formations.

The increased production has been a mixed blessing for the gas industry. Wholesale gas prices are also now below crude oil prices for equivalent amounts of energy.

Chenier's deal to sell gas overseas, and any others that follow, would tighten the surplus supplies and boost prices.