Republicans fear uncertain scope of Keystone study WASHINGTON/CALGARY, Alberta (Reuters) - The scope of a planned environmental review of the Keystone XL oil pipeline from Canada could go beyond a small disputed portion in Nebraska and threatens to delay the project further, its Republican backers in Congress said on Friday. The State Department asked on Friday for public comments by the end of July to help determine the scope of an environmental review ordered earlier this year for the controversial pipeline. The review is designed to supplement a "final" environmental impact report issued last August. Republicans suggested the State Department request could expand the review beyond an 88-mile (140-km) portion of the route through Nebraska that has been altered because of environmental concerns. "In essence they're saying, 'OK, now we're going to start all over again,'" Senator John Hoeven, a Republican from North Dakota, said in an interview. "Who knows how long it's going to take them?" said Hoeven, who has championed efforts in Congress to get fast-track approval for the project. TransCanada Corp's pipeline was designed to carry crude from Canada's oilsands and from the Bakken oilfields in North Dakota and Montana to Texas refineries. After four years of environmental reviews, and months of high-profile protests from environmental groups, President Barack Obama put a hold on the project in January. Obama said concerns raised by Nebraska, where the pipeline was initially proposed to go over a sensitive aquifer, warranted additional study, although he did allow the southernmost leg of the pipeline to go ahead. Republican presidential candidate Mitt Romney has made the pipeline part of his stump speeches, saying he would immediately approve the project if elected because of the construction jobs it would create and the oil it would bring from Canada. The State Department notice could further aggravate tensions among lawmakers trying to negotiate a new transportation spending law by June 30. Republicans want to include a provision to speed approval of the pipeline as part of the $109 billion Senate-passed package for road, bridge and rail projects. "Keystone needs to be part of it," said Hoeven, who is part of the Senate-House panel negotiating the package. TransCanada downplayed the potential of additional delay, noting the State Department's notice indicated the review would be a "supplement" to the final environmental impact study completed in August 2011. "By its terms, this does not represent a restart of the entire (environmental review) process," said Shawn Howard, a spokesman for TransCanada. The only new element needing review was the revised route through Nebraska, the company said. The State Department said its study would focus on the new Nebraska route but could also examine any other new significant environmental concerns. The department reiterated on its website that it would need until the first quarter of 2013 to complete the review process. "We will conduct our review efficiently, using existing analysis as appropriate," the department said. The State Department also said it would look at the pipeline's impact on any national historic places or "cultural resources." But Fred Upton, the Republican chairman of the House of Representatives' Energy and Commerce Committee, said the review's parameters were not yet clear. "By not limiting the scope of the review to just the new Nebraska segment, the entire project could become tangled in unnecessary review and red tape, and subjected to attacks and stalling tactics by opponents," Upton said in a statement. The National Wildlife Federation wants the State Department to take a hard look at the project, Joe Mendelson, the group's director of climate and energy policy, said in a statement. "For starters, the State Department must thoroughly analyze the safety issues involved with transporting corrosive tar sands in the pipeline, account for the increased carbon emissions that will speed global warming," Mendelson said. The group also wants additional study of risks to endangered species and more consultation with American Indian tribes, he said.