Democratic Sen. Richard Blumenthal of CT, who is on the Senate Judiciary Committee that holds hearings on Supreme Court nominees, told ABC News Chief Anchor George Stephanopoulos on "This Week" that Trump has "outsourced" his decision to the Federalist Society and the Heritage Foundation.
He said Kavanaugh would be his top choice to replace retiring Justice Anthony Kennedy.
"We are close to making a decision", Trump said.
Mr. Thapar was on the shortlist of candidates after Judge Antonin Scalia died in 2016.
While the U.S. Senate once required a 60-vote supermajority to overcome blocking tactics against Supreme Court nominees, the Republican majority changed the rules previous year during the debate on Justice Neil Gorsuch.
"Let's say it's the four people", Trump said.
Battle lines have been drawn over the future of abortion in America on the eve of President Trump's nomination of a second justice to the USA supreme court that could put the landmark 1973 ruling Roe v Wade in jeopardy.
This will be 6.30 am - Tuesday - local India time on July 10.
"If we put another two or perhaps three justices on". I think they're all outstanding. Those are very terrific people.
In his conversations over the weekend, Trump expressed renewed interest in Hardiman - the runner-up when Trump nominated Gorsuch, said two people with knowledge of his thinking who were not authorized to speak publicly.
He said he believes that any of the four candidates on the short list will dismantle Roe v. Wade and other hard-fought rights. On Sunday there was no indication that he had yet made his decision, as speculation continued to swirl around the appointment.
Ilyse Hogue, president of the pro-abortion organization Naral, told Fox News Sunday that Trump had changed the rules of the game.
The son of Indian-American immigrants, Thapar is the Nation's first Article III judge of South Asian descent.