WASHINGTON (REUTERS) - US Chief Justice John Roberts on Wednesday (Nov 21) pointedly defended the independence of the federal judiciary a day after President Donald Trump called a judge who ruled against his policy barring asylum for certain immigrants an "Obama judge" but Trump swiftly rejected the rebuke.

The remarks by Roberts represented his first public response to Trump over the Republican president's persistent criticism of the federal courts. Opponents of Trump have called his criticism of judges an attack on the rule of law in the United States.

"We do not have Obama judges or Trump judges, Bush judges or Clinton judges," Roberts, a conservative who was appointed by Republican former President George W. Bush, said in a statement released by the Supreme Court in response to a news media inquiry.

"What we have is an extraordinary group of dedicated judges doing their level best to do equal right to those appearing before them. That independent judiciary is something we should all be thankful for," Roberts added, though his statement did not mention Trump by name.

In a Twitter post, Trump wrote in response: "Sorry Chief Justice John Roberts, but you do indeed have 'Obama judges,' and they have a much different point of view than the people who are charged with the safety of our country."

It is unusual for a US chief justice, who presides over the nine-member US Supreme Court, to issue such a statement in response to a president. The US Constitution established the federal judiciary as a co-equal branch of government with the executive and legislative branches as part of a system of checks and balances on power. Presidents nominate federal judges and the Senate confirms them.

Ilya Somin, a law professor at George Mason University in Virginia, said Roberts' unusual direct response to Trump "is sending up a signal that Trump has gone beyond the pale of responsible political discourse".

"For a long time the chief justice didn't respond to it. I suspect at some point Roberts decided enough was enough and he had to say something," Somin added.

OATH OF OFFICE

Roberts, who administered the oath of office to Trump when he was sworn in as president last year, has himself been the target of Trump's attacks, in particular because of a 2012 ruling that preserved Obama's signature domestic policy achievement, the Affordable Care Act, dubbed Obamacare.

In a tweet after that ruling, Trump wrote, "Congratulations to John Roberts for making Americans hate the Supreme Court because of his BS".

Trump on Tuesday took aim at US District Judge Jon Tigar in San Francisco, who on Monday temporarily blocked an order by the president that barred asylum for immigrants who enter the country illegally from Mexico, the latest courtroom defeat for Trump on immigration policy. Tigar was appointed by Democratic former President Barack Obama.

"This was an Obama judge," Trump said. "And I'll tell you what. It's not going to happen like this anymore."

Trump also blasted the entire San Francisco-based 9th US Circuit Court of Appeals, which hears appeals from federal courts in nine western states including California.

Trump called the 9th Circuit unfair and a "disgrace".

That court has ruled against Trump's administration in several high-profile cases including his travel ban targeting people from several Muslim-majority countries and his bid to rescind a program that protects from deportation hundreds of thousands of illegal immigrants brought into the country as children.

In a Twitter post on Wednesday, Trump heaped scorn on the idea that the 9th Circuit "was indeed an 'independent judiciary'" and said its rulings "are making our country unsafe! Very dangerous and unwise!".

Judges in that region have also blocked construction of the Keystone XL pipeline project Trump has championed, and his administration's effort to restrict the military service of transgender troops.

In the asylum case, Tigar issued a temporary restraining order against the asylum rules, calling them an "extreme departure" from prior practice.

Trump last year referred to a jurist who ruled against him on his travel ban as a "so-called judge".

Trump as a presidential candidate in 2016 said a judge in a case involving Trump University was biased against him because of the jurist's Mexican-American heritage.

With the help of a Senate controlled by his fellow Republicans, Trump has appointed a succession of conservative judges in a bid to move the federal judiciary to the right. His appointments of Brett Kavanaugh and Neil Gorsuch to the Supreme Court have solidified its conservative majority for perhaps years to come.

Roberts issued his statement in response to a request for comment from the Associated Press about Trump's Tuesday remarks.