US Supreme Court nominee Amy Coney Barrett has said she is "honoured and humbled" to be President Trump's pick for a place in the top court during a tense Senate confirmation hearing.
The 48-year-old conservative jurist vowed to judge legal cases impartially.
But her selection so close to the 3 November presidential election has sparked a fierce political battle.
The panel's Republican chairman has predicted a "contentious week" of questioning ahead.
Judge Barrett's approval would cement a 6-3 conservative majority on the nine-member court, altering the ideological balance of the court for potentially decades to come.
Mr Trump picked Judge Barrett to replace liberal Justice Ruth Bader Ginsburg, who died last month aged 87.
"I have been nominated to fill Justice Ginsburg's seat, but no one will ever take her place," Mrs Barrett told senators in her opening statement on Monday. "I will be forever grateful for the path she marked and the life she led."
However, conservative views and decisions from the bench she has delivered as a judge on the Seventh Circuit Court of Appeals - of which much can be seen as opposing to the philosophy of the late Justice Ginsburg - will be heavily scrutinised by Democrats who oppose her confirmation.
The Republicans - who currently hold a slim majority in the US Senate, the body that confirms Supreme Court judges - are trying to complete the process before Mr Trump takes on Democratic rival Joe Biden in the election.
The court's nine justices serve lifetime appointments, and their rulings can shape public policy on everything from gun and voting rights to abortion and campaign finance.