The United States is on course to meet its greenhouse gas reduction target of 17 percent below 2005 levels by 2020, said Energy Secretary Ernest Moniz.

"About half of that progress we have made is from the natural gas boom, in this case the market-driven substitution for coal," Moniz told reporters Thursday during a session hosted by the Christian Science Monitor in Washington, The Hill reports.

"Eventually, if we are going to get down to really low-carbon emissions, natural gas, just like coal, would need to have carbon capture," said Moniz, who was confirmed as energy secretary in May. "But that looks to be quite a ways off. In the meantime, gas will actually be part of the solution."

The energy department's analytical arm, the Energy Information Administration, last week said that fossil fuels are expected to continue supplying much of the energy used globally.

Noting that "natural gas is the fastest growing fossil fuel in the outlook," EIA said global natural gas consumption corresponds with production gains seen from shale and other unconventional deposits.

As for concerns regarding possible dangers of hydraulic fracturing, or fracking, a process which involves massive amounts of water, sand and chemicals injected at high pressure to fracture rock and release stored gas, Moniz said, "to my knowledge, I still have not seen any evidence of fracking per se contaminating groundwater."

Yet the secretary acknowledged other environmental concerns and challenges associated with natural gas development including poor completion of wells, surface spills of so-called flowback water, methane emissions and air quality problems around production sites.

"All of these are manageable. We know what to do about completing a well, etc., but manageable still has the requirement of being managed, being managed all the time," Moniz said, noting the need for regulations, enforcement of them, and "self-enforcement" by the industry.

Regarding exports of natural gas, the secretary during the event with reporters said the Obama administration is "working hard" to evaluate such proposals, the Houston Chronicle reported.

"We've committed to trying to do expeditious review -- case-by-case -- in the order as declared by the Department of Energy in 2012."

While the Energy Department has approved two applications to export natural gas to countries that do not have free-trade agreements with the United States, 15 other applications are awaiting a decision, with proposals to export as much as 29 billion cubic feet of natural gas to non-free-trade partners.

In a letter to Moniz last month, 34 senators urged the secretary to make decisions on the remaining applications "in an expeditious manner," noting lengthy reviews could jeopardize the nation's ability to retain a competitive position against other natural gas-exporting countries.