US President Barrack Obama has nominated court of appeals judge Merrick Garland to the Supreme Court, replacing Antonin Scalia.
Garland is viewed as a moderate and has received support from both Democrats and Republicans in his career.
“I’ve selected a nominee who is widely recognised not only as one of America’s sharpest legal minds, but someone who brings to his work a spirit of decency, modesty, integrity, even-handedness, and excellence,” said Obama.
Garland called the nomination the "greatest honour of [his] life".
Scalia, who died last month, was one of the court's strongest conservative voices.
The appointment may not be approved however as the Republican majority Senate has vowed to block any nomination from Obama.
Majority leader of the Senate Mitch McConnell said he will not meet with judge Garland and Republicans will not confirm Garland's nomination.
Many Republican's think the nomination should be left to the next US President, who will be elected in November.
Property tycoon Donald Trump is currently leading the field for the Republican nomination, while former secretary of state Hilary Clinton is likely to take the Democrat nomination.
“It is a President's constitutional right to nominate a supreme court justice,” McConnell said. “And it is the Senate’s constitutional right to act as a check on a President and withhold its consent.”
Scalia's death left the Supreme Court balanced equally between Democrats and Conservatives, with four left leaning members and four leaning to the right.
The US Supreme Court, the country's highest, often has final say on issues such as abortion, immigration and climate change, making appointments politically divisive.
“Of the many powers and responsibilities that the Constitution invests in the presidency, few are more consequential than appointing a Supreme Court justice," Obama said at the announcement ceremony at the White House. "The men and women who sit on the Supreme Court are the final arbiters of American law."
This is the third nomination to the Supreme Court from Obama since he became President in 2009.