TransCanada Corp. announced Tuesday that it has pushed back the possible startup date of the Keystone XL pipeline to sometime in early 2015.

The company advertised the new date in an earnings release, according to The Associated Press. The release said TransCanada executives are continuing to work with Nebraska officials to settle on an alternative pipeline route that avoids the state's Sandhills region, the home of the environmentally sensitive Ogallala Aquifer.

After announcing it would withhold approval for the pipeline until after the 2012 presidential election, the Obama administration ultimately rejected TransCanada's permit application last month when Republican legislators tried to force the president to make a final decision. The administration said a 60-day deadline imposed by the lawmakers would not allow enough time to conduct necessary environmental impact studies.

TransCanada insists the administration's denial was not based on the merits of the pipeline and said it will reapply for a permit to begin construction. Last month, TransCanada said it expected the new application would be processed in an expedited manner so that the pipeline could be in service in late 2014.

Keystone XL would transport crude oil from the tar sands of Alberta, Canada, to refineries in the Gulf Coast of the U.S. The project has been vehemently opposed by environmental groups,  who maintain the project could result in potentially devastating oil spills and increased levels of greenhouse gas emissions.

Senate Republicans, who insist the project would yield substantial job creation, introduced an amendment to a federal transportation bill on Monday that would speed up the construction and operation of the Keystone XL. It is unclear as to how quickly the amendment, reportedly backed by 44 Republicans and one Democrat, will be up for a vote.

A coalition of environmental and progressive organizations kicked off a 24-hour campaign on Monday that aimed to send 500,000 e-mail messages in opposition to the pipeline to members of the U.S. Senate. Leaders of 350.org, one of the primary sponsors of the event, report the event reached its goal in less than seven hours, and ultimately surpassed 777,000 messages by the 24-hour mark.