The US Senate is expected to confirm conservative judge Brett Kavanaugh as the next Supreme Court justice yesterday -- offering President Donald Trump a big political win and tilting the nation's high court decidedly to the right.

The months-long battle over Kavanaugh's nomination has gripped Washington, laying bare the partisan gridlock on Capitol Hill and the political polarisation of America just a month before midterm elections.

The Senate vote, set to begin from 3:30 pm (1930 GMT), will bring an end to a raucous nomination process defined by harrowing testimony from a woman who says Kavanaugh tried to rape her when they were teenagers -- and his fiery rebuttal.

Joe Manchin

If Kavanaugh is confirmed, Trump will have succeeded in having his two picks seated on the court -- a major coup for the Republican leader less than halfway through his term.

His promotion to the Supreme Court will also stand as a demoralising defeat for Democrats who battled hard to block the 53-year-old judge at all costs.

Kavanaugh's confirmation was all but sealed on Friday when he won the support of key Senate Republican Susan Collins and conservative Democrat Joe Manchin.

Their statements of support brought the number of senators supporting Kavanaugh to 51 in the 100-member chamber.

Kavanaugh's nomination as a replacement for retiring justice Anthony Kennedy was controversial from the start -- but the initial focus was solely on the conservative views held by the married father of two.

If he wins confirmation, Kavanaugh -- who has faced a bruising process that raised questions over his candor, partisan rhetoric and his lifestyle as a young man -- will seal a conservative majority on the nine-seat high court, possibly for decades to come.

His nomination has been met with loud protests, both in Washington and in other cities across the United States. On Friday, more than 100 people were detained.

Alaska Senator Lisa Murkowski was the only Republican to break ranks.

She described her decision to oppose Kavanaugh as "agonizing," and said that while she hopes he will be a "neutral arbiter" on the court, he was not "the right person for the court at this time."