WASHINGTON - US Supreme Court nominee Neil Gorsuch on Tuesday pledged independence from President Donald Trump, bristled at his criticism of the judiciary and said not even the president is above the law, amid Democratic concerns he would be beholden to the man who selected him.

Answering questions from senators during the second day of his Senate Judiciary Committee confirmation hearing, Gorsuch said Trump never asked him to overturn the 1973 Supreme Court ruling legalizing abortion nationwide, saying if the Republican president had done so, "I would have walked out the door."

Trump promised during last year's presidential campaign to appoint an anti-abortion justice who would overturn the landmark Roe v. Wade ruling, which many conservatives want reversed.

If confirmed by the Senate as expected to fill a 13-month-old vacancy, Gorsuch would restore the nine-seat court's conservative majority at a time when Republicans control Congress and the White House. But the conservative federal appeals court judge from Colorado repeatedly said he was beyond politics.

"When I became a judge, they gave me a gavel, not a rubber stamp," Gorsuch said. "I am my own man," he added.

Trump has assailed the judiciary both as a candidate and since taking office on Jan 20. He condemned federal judges who have put on hold his two executive orders to ban the entry into the United States of people from several Muslim-majority countries, calling one a "so-called judge" and suggesting that blame for a future terrorist attack should go to the courts.

"When anyone criticizes the honesty or integrity or the motives of a federal judge, well I find that disheartening, I find that demoralizing, because I know the truth," Gorsuch said.

When Democratic Senator Richard Blumenthal asked if that includes Trump, Gorsuch said, "Anyone is anyone." Gorsuch previously made similar remarks in private to senators including Blumenthal, but Trump at the time accused Blumenthal of misrepresenting Gorsuch's comments.

Gorsuch's steady, measured performance during the marathon session, marked by a few moments of indignation under Democratic questioning, indicated he was on track for confirmation.

Democrats probed Gorsuch on whether he would be willing to hold Trump accountable.

Asked by Senator Patrick Leahy whether a president has the power to violate a law on surveillance of Americans, Gorsuch said, "Nobody is above the law in this country, and that includes the president of the United States."

Republican Senator Lindsey Graham said that if Trump resumes the use of waterboarding, a prohibited form of simulated drowning, on detainees, he "may get impeached".

Gorsuch said he would not speculate on whether Trump could be prosecuted if he authorized waterboarding, but repeated, "No man is above the law."

Republicans have praised Gorsuch, 49, as highly qualified for a lifetime appointment as a justice. Democrats, who have slim chances of blocking his nomination, have questioned his suitability, with some portraying him as favoring corporate interests and insufficiently independent from Trump.

"I have offered no promises on how I'd rule in any case to anyone. And I don't think it's appropriate for a judge to do so, no matter who's doing the asking," Gorsuch added.

Gorsuch refused to offer his opinion of Trump's travel ban, saying it was an ongoing case.