* White House rules out using 14th Amendment on debt limit
* Obama has no "luxury" to debate constitutional law
* Only Congress has authority to borrow - White House
By Alister Bull
WASHINGTON, July 26 (Reuters) - President Barack Obama will not use a clause in the U.S. Constitution to bypass Congress and raise the federal government's debt limit on his own, the White House said on Tuesday.
"It's not available," White House press secretary Jay Carney said in the administration's firmest dismissal of the 14th Amendment as a way to avoid a U.S. default if Congress fails to lift the $14.3 trillion debt limit by an Aug. 2 deadline.
"The Constitution makes clear that Congress has the authority, not the president, to borrow money and only Congress can increase the statutory debt ceiling. That is just a reality."
The 14th Amendment stipulates the U.S. public debt "shall not be questioned" -- which some legal scholars argue would allow Obama, a Democrat, to sidestep lawmakers and raise the borrowing limit on his own.
The White House has persistently poured cold water on the idea that a provision in the Constitution stemming from the Civil War in the 1860s to make sure Union debts were honored and Confederate obligations were not could be a way around the debt impasse.
But some influential Democrats have continued to see it as a legitimate strategy to sidestep a Congress deadlocked over the debt limit because of fiscally conservative Tea Party Republicans who will not compromise on any tax increases.
Former President Bill Clinton, a Democrat, has said that if it came to averting a U.S. default, he would invoke the 14th Amendment, raise the debt ceiling and "force the courts to stop me."
Obama played down this notion on Friday, when he said White House lawyers were "not persuaded that that is a winning argument." But his remarks did signal the 14th Amendment route was at least being reviewed by his administration.
That impression remained intact after comments by Treasury Secretary Timothy Geithner on Sunday that bypassing Congress was "not a workable option," which also appeared to stop short of a flat-out rejection.
On Tuesday, Carney went out of his way to rule it out.
"You can have an esoteric discussion about constitutional law and what could not or should not be," he said. "But we don't have the luxury or the time. The law is as it is. That is how we view it and that is why we have to reach a compromise." (Additional reporting by Laura MacInnis and Caren Bohan; Editing by John O'Callaghan)