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While the Obama administration says it needs more time to assess the potential risks surrounding the proposed Keystone XL pipeline, a vast underground network of more than 2 million miles of energy pipeline already traverses the United States.

Several energy experts who represent the oil and gas industry say the controversial Keystone XL, a 1,700-mile pipeline that would run from Canada to Texas, poses less of a risk to the environment than the estimated 50,000 miles of crude oil pipelines already crisscrossing the U.S., a network they say is safe and efficient.

The Obama administration on Wednesday blocked a permit for the $7 billion Keystone XL, at least temporarily, claiming a more thorough review is needed to examine problems it may pose to the nation’s air and water quality. The administration also blamed Republicans for including a provision in a recent tax cut bill that compelled a decision within a 60-day time frame.

The pipeline system, proposed by the Canadian firm TransCanada, would transport crude oil from the Athabasca Oil Sands in northeastern Alberta to multiple locations in the U.S., including as far as the Gulf Coast of Texas. The Keystone XL would go through Montana, South Dakota, Nebraska, Kansas and Oklahoma, and the so-called “feeder pipelines” would connect it to rich oil fields in North Dakota and Montana.

The U.S. State Department has expressed concerns over the pipeline's environmental impact, particularly in the Nebraska Sandhills, an area of porous hills that includes a high concentration of wetlands and a key aquifer.

Environmental activist groups claim the pipeline system could pollute air and water supplies as well as harm fragile ecosystems. The original route also called for the pipeline to cross the Ogallala Aquifer, one of the world’s largest aquifers that extends into eight states and provides drinking water for two million people.

“It will be environmentally and economically devastating if there were to be a spill,” Kim Huynh, a spokeswoman for Friends of the Earth, told FoxNews.com. “We think that Keystone XL pipeline would be dirty at both ends and certainly dangerous in between.” She described tar sands oil as "the world’s dirtiest oil" that she said “needs to stay in the ground.” Huynh also said the air surrounding oil refinery communities adds “immense amount of air pollution that causes lung disease and other detrimental health impacts.”

But several energy experts say the Keystone XL would be no different from an extensive network of energy pipelines already in place – and some say its state-of-the-art design would make it safer than many of the country’s aging pipelines.

“There’s no shortage of energy pipelines,” Dan Kish, senior vice president for policy at the Institute for Energy Research, told FoxNews.com. “This pipeline would be better than 1.9 million miles of pipeline already in the United States. It’s newer and has the best technology.”

Maps of the U.S. energy pipeline system show a vast abundance of crude oil pipelines crossing through states like Montana to Minnesota to Texas.

Major oil pipelines include a 9,467-mile network operated by Magellan Pipeline Co. LLC; a 7,833-mile system owned by MidAmerican Energy Company; and 7,646 miles of pipeline owned by Plains All-American Pipeline LP. Other top oil pipeline companies include ConocoPhillips with 6,027 miles and Colonial Pipelines with 5,596 miles.

Kish said underground pipelines are the safest way to transport crude oil, though he acknowledged that “whenever you have any kind of human endeavor, you have potential problems and they do occur.”

“We have tens of thousands of pipeline and I don’t think there’s any good evidence that pipelines are a significant impact on ecosystems to the point that they can’t adapt,” said Kenneth Green, resident scholar at the American Enterprise Institute.

Kish and Green said the alternative to pipeline systems is to transport the oil by tanker, train or truck – all of which they said pose a considerably higher risk for accident and spillage and cost far more in the long run.

“Do we tell Canada to move the oil to Texas by truck?” Green asked.

Robert Schulz, a professor at the University of Calgary's Haskayne School of Business, said a common “misperception” held by many environmental activists is that oil from Canada is “dirtier” than crude that comes from other parts of the world.

But, Schulz argued, the contaminants in Canadian oil -- – particularly CO 2 – are reasonably similar to those coming from oil sources in Venezuela and the Middle East.

“Eighty-four percent of the environment’s contaminants come from a car tail pipe -- not from producers. So if they [activists] really had a problem, they wouldn’t drive their cars,” added Schulz.

TransCanada has promised to reapply for a presidential permit after finding a route through Nebraska that would circumvent sensitive areas.

Nebraska Gov. Dave Heineman, a Republican, and other state lawmakers had expressed concern over Keystone’s original route because of its close proximity to the state’s water supply. But Heineman told Fox News on Thursday that he’s confident an alternative route being worked out with TransCanada will not pose a risk to environmentally sensitive areas and should certainly meet federal approval.

"I fully expect we could get it done, certainly in the early September, August timeframe," Heineman told Fox News. "I would send the letter back to the president of the United States saying we approve it and if he were decisive, he could turn around and approve it shortly thereafter, well before the November election."

FoxNews.com's Cristina Corbin and the Associated Press contributed to this report.