WASHINGTON (Reuters) - Lawmakers ratcheted up pressure on the Obama administration on Tuesday to speed approval for companies to export natural gas, arguing it would help relieve a glut dampening output of the fuel.

The Department of Energy, or DOE, "does not seem to have a set timeline for decisions or a sense of urgency," about approving exports of liquefied natural gas, or LNG, Representatives Gene Green, a Texas Democrat, and James Lankford, an Oklahoma Republican, said in a letter to Energy Secretary Steven Chu.

"Our region and our country need an outlet for natural gas production," Green and Lankford said in a letter signed by 44 House lawmakers from Texas, Oklahoma, Louisiana and Arkansas, 10 of whom were Democrats.

The U.S. natural gas surplus "has produced very low prices for producers and an absence of market opportunities for natural gas, leading many wells to be shut in," the letter said.

It was the second real push from Capitol Hill in support of LNG exports after a group of lawmakers from states rich in shale gas wrote Chu in late June.

The U.S. natural gas revolution, spurred by wide development of hydraulic fracturing, or fracking, directional drilling and other technologies, has brought with it a push to build export terminals to send the fuel to markets in Asia and Europe where prices for gas are far higher.

The department is allowed to quickly approve applications to export gas to South Korea, Chile and more than a dozen other countries that have free-trade agreements with the United States. Applications for exports to countries that do not have the agreements with Washington require a more thorough process.

The Energy Department has only approved full export rights for one project, Cheniere Energy Inc's Sabine Pass, terminal.

The department said it would wait on the results from a study of implications of exports on the U.S. economy before acting on eight other applications from Dominion Resources Inc and other companies.

The delay has given presumed Republican candidate for president Mitt Romney's campaign some fodder to criticize the Obama administration for the delay.

Critics say approving gas exports could significantly raise fuel prices and costs for U.S. home owners and gas-dependent businesses. They say the chemicals and other industries that have begun to announce plans to build plants again in the United States, could be hurt if exports boosted prices.

Green and the other lawmakers wrote that each of the ports will require thousands of jobs and billions of dollars in investments. But the investments "cannot be made or fully supported without predictable timelines for decision making by the Department," the letter said.

The DOE would not estimate on Tuesday when it would decide on the exports. The administration "is focused on continuing to expand domestic production of our natural gas resources, which are currently at an all-time high," said spokeswoman Jen Stutsman.

A source at the DOE previously said the two-part study on exports and the U.S. economy would be released in late summer and decisions on the ports would follow a public comment period.

(Reporting by Timothy Gardner; editing by Marguerita Choy and Andre Grenon)