DENVER -- The U.S. energy boom is blurring the traditional political battle lines across the country.

Democrats are split between environmentalists and business and labor groups, with the proposed Canada-to-Texas oil pipeline a major wedge.

Some deeply conservative areas are allying with conservationists against fracking, the drilling technique that's largely responsible for the boom.

The divide is most visible among Democrats in the nation's capital, where 11 Democratic senators wrote President Barack Obama this month urging him to approve the Keystone XL pipeline, which is opposed by many environmental groups and billionaire activist Tom Steyer. The State Department said Friday that it was extending indefinitely the amount of time that federal agencies have to review the project, likely delaying a pipeline decision until after the November elections.

Crossing party lines

Several senators from energy-producing states such as Louisiana and Alaska have distanced themselves from the Obama administration, while environmental groups complain the president has been too permissive of fracking.

There is even more confusion among Democrats in the states as drilling rigs multiply and approach schools and parks.

California Gov. Jerry Brown was shouted down at a recent state convention by party activists angry about his support for fracking. New York Gov. Andrew Cuomo has kept fracking in his state in limbo for three years while his administration studies health and safety issues. In Colorado, Gov. John Hickenlooper has drawn environmentalists' ire for defending the energy industry, and a ballot battle to regulate fracking is putting U.S. Sen. Mark Udall in a tough situation.

But the issue cuts across party lines.

Even in deeply Republican Texas, some communities have restricted fracking. In December, Dallas voted to effectively ban fracking within city limits.

"You're looking at a similar boom as we had in tech in 1996," said Joe Brettell, a GOP strategist in Washington who works with energy companies. "The technology has caught up with the aspirations, and that changes the political dynamics fundamentally."

Those technological advances have made it possible for energy companies to tap deep and once-untouchable deposits of natural gas and oil. They include refinements in hydraulic fracturing, or fracking, which is the injection of chemicals into the ground to coax buried fossil fuels to the surface.

U.S. top oil producer?

The U.S. is now the world's largest natural gas producer and is expected to surpass Saudi Arabia soon as the world's greatest oil producer, becoming a net exporter of energy by 2025.

The boom has brought drilling rigs into long-settled neighborhoods, raising fears of water contamination, unsafe traffic and air pollution, and outraging residents.

Pollster Steven Greenberg said Cuomo provides little notice before his public appearances because anti-fracking protesters will crash his events. Republicans blame the governor for stymieing growth. New York voters split evenly on fracking, with Democrats only modestly more likely to oppose it than Republicans.

"No matter what he decides, he's going to have half the people upset with him," Greenberg said. "From a purely political point of view, it's hard to argue with his strategy -- punt."

In California, Brown has a long record of backing environmental causes, but he's drawn the wrath of some environmentalists for supporting fracking. One group cited the $2 million that oil and gas companies have given the governor's causes and campaigns since 2006. Democrats in the Legislature have proposed a freeze on fracking but are not optimistic Brown will support it.

The Democratic split is sharpest in Colorado.

Hickenlooper, a former oil geologist, has been a staunch supporter of fracking; at one point he said he drank fracking fluid, albeit a version without most of the hazardous chemicals. His administration has fought suburban cities that have banned fracking, insisting that only the state can regulate energy exploration.

In response, activists are pushing 10 separate ballot measures to curb fracking. One measure would let cities and counties ban it.