U.S. Supreme Court Justice Antonin Scalia, the longest-serving justice on the high court, is dead.
Scalia died in his sleep of natural causes at Cibolo Creek Ranch, a resort in southwest Texas.
The conservative Scalia was 79 years old. He was appointed to the high court by President Ronald Reagan in 1986.
Chief Justice John Roberts, in confirming Scalia's death, called him an "extraordinary individual and jurist, admired and treasured by his colleagues."
Texas Gov. Gregg Abbott, who first announced Scalia's death, called him "an unwavering defender of the written Constitution and the rule of law...a solid rock who turned away so many attempts to depart from and distort the Constitution."
"A lion of American law has left the stage," U.S. Attorney General Loretta Lynch said in a statement, "and it is up to all of us – every American – to keep our national constitutional dialogue as lively and as learned as he left it.”
Former president Bill Clinton noted that even though he and Scalia "disagreed on nearly everything, I always kind of liked Justice Scalia because he never pretended to be anything he wasn’t. He was very straightforward about what he believed..."
Former president George W. Bush said Scalia " brought intellect, good judgment, and wit to the bench, and he will be missed by his colleagues and our country."
Watch: President Obama's Statement on Death of Justice Scalia
Obama to nominate replacement
President Barack Obama said he plans to "fulfill my constitutional responsibility to nominate a successor in due time," and said he expects the Senate to give the nominee a timely hearing and a vote.
Obama called Scalia a brilliant legal mind who profoundly shaped the legal landscape and one of the most consequential judges every to serve on the bench.
He said there is plenty of time to find a replacement for Scalia and the Senate had a responsibility to give that nominee a fair hearing and timely confirmation vote.
"These are responsibilities that I take seriously as should everyone," he said. "They're bigger than any one party. They are about our democracy."
FILE - In this June 17, 1986 file photo, President Ronald Reagan announces the nomination of Antonin Scalia, left, to the Supreme Court. William Rehnquist is at right.
Filling the vacancy
Even before the president spoke Saturday evening, U.S. Senate Majority Leader Mitch McConnell, a Republican, voiced opposition to President Obama nominating a successor.
"The American people should have a voice in the selection of their next Supreme Court justice. Therefore, this vacancy should not be filled until we have a new president," McConnell said said Saturday.
Obama would almost certainly nominate a liberal to the court. McConnell is banking on a Republican winning the presidency in November and naming a conservative.
With Scalia, the conservatives on the court enjoyed a slim 5-4 majority, although Justice Anthony Kennedy occasionally voted with his more liberal colleagues, most notably on the recent case the made gay marriage legal in the United States.
But the top Democrat on the Senate Judiciary Committee, Patrick Leahy, said Obama and the Senate have a constitutional duty to fill vacancy in the bench.
"The Supreme Court of the United States is too important to our democracy for it to be understaffed for partisan reasons. It is only February," Leahy said.