The Republican-led Congress sent the bill to the president on February 24.
White House spokesman Josh Earnest said President Barack Obama vetoed the bill “without any drama or fanfare or delay”.
The 875-mile pipeline would carry tar sands oil from Alberta, Canada, to Nebraska where it joins pipes running to Texas.
The project has pitted Republicans and other supporters, who say it will create much needed jobs, against many Democrats and environmentalists, who warn the pipeline will add to carbon emissions and contribute to global warming.
The Keystone bill is Barack Obama’s third veto as president and his first since Republicans won full control of Congress in November.
More vetoes are expected in the coming months as Republicans in Congress craft legislation to reverse Barack Obama’s action on health care, immigration and financial regulation.
The Keystone XL pipeline project was first proposed more than six years ago, but has languished, awaiting a permit required by the federal government because it would cross an international boundary.
The White House has said the bill passed by Congress interfered with the normal permitting process.
Without a veto-busting majority in Congress, Republicans are considering inserting Keystone into other critical legislation dealing with energy, spending or infrastructure in the hope that Barack Obama would be less likely to veto those priorities.
OMoTlO2Qjh0President Joe Biden has urged pro-Palestinian protesters on university campuses to uphold the rule of…
Blue Ivy Carter has joined the voice cast of The Lion King prequel Mufasa: The…
At least five people, including a four-month-old baby, have been killed after dozens of tornadoes…
Harvey Weinstein has been hospitalized just days after his 2020 rape conviction in New York…
Hamas has published a video showing the first proof of life of US and Israeli…
Prosecutors and Donald Trump’s attorneys delivered opening statements and the first witness was called on…