Key dates of controversial Keystone XL oil pipeline

The fate of the controversial Keystone XL pipeline, a $7 billion project to bring oil from Canada's tar sands all the way to refineries in the US state of Texas, will be debated at a public hearing in Nebraska Thursday.

Here are key dates in the pipeline's development.

- July 2008: TransCanada announces plans to build a 3,200-kilometer (1,980-mile) pipeline to transport oil from Alberta's tar sands to refineries on the Texas coast. The Keystone XL would be an expansion of a system already under construction and the plan is to nearly double capacity from 590,000 to 1.1 million barrels per day.

- March 2010: The Canadian government approves a 529 kilometer (328 mile) leg of the Keystone XL pipeline that would carry up to 900,000 barrels of oil per day from Hardisty, Alberta to the Canadian/US border at Monchy, Saskatchewan.

- June 2010: TransCanada begins operations on the initial Keystone pipeline, which transports oil from Alberta to refineries in Oklahoma and Illinois.

- August 2011: The US State Department issues a draft report stating that Keystone XL would have "no significant impact" on the environment, sparking disbelief from activists who demand that President Barack Obama deny approval of the permit.

- November 2011: Obama's administration says it will put off a decision on the Keystone XL project, which pits environmentalists against labor unions and business interests in his political base, until after the November 2012 presidential elections. The State Department cites concerns about the impact on Nebraska's environmentally-sensitive Sand Hills region and says it is considering whether a new route is needed.

- December 2011: Obama's political rivals pass a bill requiring he make a decision on the pipeline within 60 days amid intense election-year posturing.

- January 2012: Obama rejects the Keystone XL pipeline, saying he could not vouch for its safety in such a short amount of time, and suggests TransCanada resubmit its permit application.

- February 2012: TransCanada announces it will go ahead with building part of the pipeline between Oklahoma and the Texas coast that does not require US presidential approval.

- May 2012: TransCanada resubmits its application to the US State Department with a new route that avoids Nebraska's Sand Hills and does not include the southern portion of the project. The pipeline awaiting approval is now just the 1,897 kilometers (1,179 miles) portion from Hardisty, Alberta to Steele City, Nebraska with an estimated cost of $5.3 billion and capacity of 830,000 barrels per day.

- August 2012: TransCanada begins construction on the southern portion of the pipeline from Cushing, Oklahoma to the Houston and Nederland, Texas areas. The initial capacity of the Gulf Coast Pipeline will be 700,000 barrels of oil per day, with the ability to increase to 830,000 barrels per day. It is expected to be operational in late 2013.

- January 22, 2013: Keystone XL clears a key hurdle after the governor of Nebraska approved the new route that avoids the environmentally sensitive Sand Hills, which includes a high concentration of sensitive wetlands and extensive areas of shallow groundwater.

- March 1, 2013: The US State Department issues a draft report suggesting that the rerouted Keystone XL pipeline would have no major impact on the environment, but stopped short of recommending it be approved.

- April 18, 2013: A public hearing is set to be held in Grand Island, Nebraska as a 45-day public consultation period draws to an end. The State Department will consider the input and make a final recommendation to Obama in the coming months.