Brett Kavanaugh, Donald Trump's pick for the Supreme Court, appears to check all the conservative boxes.

On Monday evening, the US president nominated the 53-year-old judge to replace retiring Associate Justice Anthony Kennedy, 81, whom Kavanaugh once clerked for.

"The Supreme Court is entrusted with the crown jewel of our republic, the Constitution of the United States," Trump said in the East Room of the White House before announcing his choice.

Trump called Kavanaugh a "judge's judge, with a clear and effective writing style".

Kavanaugh stood next to Trump with his wife, Ashley, and two young daughters.

"A judge must interpret the law, not make the law," Kavanaugh said. "A judge must interpret the Constitution as written, informed by history and precedent."

The Senate's top Democrat, Chuck Schumer, tweeted while Kavanaugh was speaking that "Judge Kavanaugh's own writings make clear that he would rule against reproductive rights and freedoms, and that he would welcome challenges to the constitutionality of the Affordable Care Act".

Schumer later added that he would fight the nomination "with everything I have".

In a series of cases, Kavanaugh, who sits on the Court of Appeals for the DC Circuit, considered the second most powerful court in the US, took approaches that likely will be agreeable to Trump's base.

In a major Second Amendment case, Kavanaugh dissented from a decision that upheld a ban on semi-automatic rifles. He also dissented from a decision that upheld the Affordable Care Act contraceptive mandate.

Kavanaugh recently sided with the Trump administration in a major abortion case, dissenting from what he called a "radical" majority opinion that invented "a new right for unlawful immigrant minors in US government detention to obtain immediate abortion on demand".

Kavanaugh also has written that presidents shouldn't have to deal with criminal investigations or civil lawsuits while in office.

Kavanaugh also worked on the Kenneth Starr investigation that led to president Bill Clinton's impeachment in 1998, which could harden the Senate Democrats' position at the hearings. Republicans currently hold a 50-49 edge in the Senate, with GOP Senator John McCain undergoing treatment for brain cancer in Arizona.

AP contributed to this story