WATCH LIVE: Robert F. Kennedy Jr. testifies at Senate confirmation hearing

WASHINGTON (Reuters) - Robert F. Kennedy Jr., President Donald Trump's pick to lead the top U.S. health agency, is set to face a grilling from Senate Democrats and Republicans on Wednesday over his views on vaccines, abortion, and potential conflicts of interest.

Kennedy, 70, will appear in front of the Senate Finance Committee at 10 a.m. ET (1500 GMT) on Wednesday. While that committee is responsible for advancing his nomination to the full Senate, Kennedy is also scheduled to appear in front of a second Senate panel that oversees health on Thursday.

The Republican-controlled Senate has not rejected any of Trump's nominees so far. His controversial defense secretary pick, Pete Hegseth, squeaked by in a 51-50 vote after Vice President JD Vance was needed to break a tie on Friday, despite concerns that the nominee was not qualified for the position, and allegations of sexual assault and alcohol abuse. 

Kennedy's nomination also will put Republican lawmakers' loyalty to the test, as the former Democrat holds a range of unorthodox positions that could alienate both conservatives and liberals.

The environmental lawyer is seen as a controversial pick on both sides of the aisle chiefly for having spread misinformation around the safety of vaccines in the past.

"I cannot recall a nominee more dangerous to the health of Americans than Mr. Kennedy," Democratic minority leader Chuck Schumer said on the Senate floor a day before Kennedy's first hearing.

"Mr. Kennedy has made a living not by promoting public health, but by actively fighting it. He is the face of the modern anti-vaccine movement, responsible for spreading fringe and outright false beliefs about vaccines," Schumer said.

Republican Senator Bill Cassidy, who chairs the Senate Health, Education, Labor and Pensions Committee that Kennedy is set to appear before on Thursday and also sits on Finance, called the nominee "wrong" on vaccines. But he said they had a "frank conversation" during Kennedy's Capitol Hill tour aimed at winning support. Cassidy is one of a handful of Republicans seen as undecided on the nomination.

While most of the opposition to Kennedy is driven by his stance on vaccines, some Republicans also object to his comments in support of abortion rights, as well as his perceived stance against the pharmaceutical industry.

In written testimony to the Finance Committee, Kennedy said he is not anti-vaccine or anti-industry and that he believes "vaccines have a critical role in healthcare." He noted that his own children had been vaccinated, according to the document seen by Reuters, but helped found the anti-vaccine group Children's Health Defense.

Kennedy says he wants to work to end chronic disease, break any ties between employees at the U.S. drugs regulator and industry, and advise U.S. water systems to remove fluoride.

He has decried the U.S. food industry for adding ingredients he says have made Americans less healthy.

Kennedy needs the support of at least 50 senators, which would allow Vance to cast another tie-breaking vote and confirm his nomination if needed. 

(Reporting by Ahmed Aboulenein in Washington; Additional reporting by Stephanie Kelly in New York; Editing by Caroline Humer and Bill Berkrot)