President Barack Obama speaks at the White House, Feb. 23, 2016, in Washington, D.C. Chip Somodevilla/Getty Images

An independent mind, integrity and a series of impeccable credentials — these are the qualifications President Barack Obama said he is looking for in the next U.S. Supreme Court justice, adding Wednesday that he expects to nominate someone in the coming weeks.

While Republican opposition is running high to Obama's plans to replace the late Justice Antonin Scalia, Obama laid out his criteria in a guest post on the SCOTUSblog website, which appears to be his first and only guest post. Obama wrote that it was his constitutional duty as president to appoint Supreme Court justices and that it was one of the biggest decisions a president can make.

“Needless to say, this isn’t something I take lightly,” Obama wrote. “It’s a decision to which I devote considerable time, deep reflection, careful deliberation and serious consultation with legal experts, members of both political parties and people across the political spectrum.”

In a potential candidate, Obama said he wants someone who has a mastery of the law and who can make clear very complex issues of law. He wrote that while he doesn’t want someone with a specific political agenda, he wants someone who can understand the limits of the judiciary — somebody who knows it is his or her job not to make law but rather interpret it.

Obama said he also wants a nominee who knows that life experiences outside the courtroom can inform a legal perspective. Obama wrote he wants someone who has a “keen understanding that justice is not about abstract legal theory, nor some footnote in a dusty casebook. It’s the kind of life experience earned outside the classroom and the courtroom; experience that suggests he or she views the law not only as an intellectual exercise but also grasps the way it affects the daily reality of people’s lives in a big, complicated democracy and in rapidly changing times.”

Obama faces an uphill battle with getting the Senate to approve a Supreme Court nominee before the end of his term, as Senate Republicans said Tuesday they would not only reject a candidate, they wouldn’t even hold confirmation hearings, the New York Times reported. GOP leaders want the next president to determine who will be the ninth justice after Scalia, a longtime member of the court’s conservative wing, died this month.

Despite having eight justices, which could lead to split decisions, the court will deal with the even number, Justice Samuel Alito said, as CNN reported. "We will see what develops," Alito said Tuesday.