The people requested anonymity because they weren't authorized to discuss the confidential interview. The meeting with Donald Trump Jr. comes after the committee's Republican chairman, North Carolina Sen. Richard Burr, subpoenaed him as part of the panel's Russia investigation.
Burr received considerable blowback from some of his GOP colleagues for the move, but he told fellow senators that Trump Jr. had backed out of an interview twice, forcing the committee to act.
Senators want to discuss answers Trump Jr. gave the panel's staff in a 2017 interview, as well as answers he gave to the Senate Judiciary Committee in a separate interview behind closed doors that year. President Trump's former lawyer, Michael Cohen, told a House committee in February that he had briefed Trump Jr. approximately 10 times about a plan to build a Trump Tower in Moscow before the presidential election. Trump Jr. told the Judiciary panel he was only "peripherally aware" of the real estate proposal.
The panel is also interested in talking to Trump Jr. about other topics, including a campaign meeting in Trump Tower with a Russian lawyer that captured the interest of special counsel Robert Mueller. Mueller's report, released in April, examined the meeting but found insufficient evidence to charge anyone with a crime.
Trump Jr.'s scheduled appearance was first reported by CNN.
Trump said in May he believed that his son was being treated poorly.
"It's really a tough situation because my son spent, I guess, over 20 hours testifying about something that Mueller said was 100 percent OK and now they want him to testify again," Trump told reporters at the White House. "I don't know why. I have no idea why. But it seems very unfair to me."
It's the first known subpoena of a member of the president's immediate family, and some Republicans went so far as to suggest Trump Jr. shouldn't comply.
Burr's home state colleague, Sen. Thom Tillis, R-N.C., tweeted, "It's time to move on & start focusing on issues that matter to Americans." Sen. John Cornyn of Texas, a GOP member of the panel, said he understood Trump Jr.'s frustration. Cornyn's Texas colleague, Republican Sen. Ted Cruz, said there was "no need" for the subpoena.
Senate Majority Leader Mitch McConnell has defended Burr, saying "none of us tell Chairman Burr how to run his committee."
Still, McConnell made it clear that he is eager to be finished with the probe, which has now gone on for more than two years.
It's uncertain when the intelligence panel will issue a final report. Burr told The Associated Press last month that he hopes to be finished with the investigation by the end of the year.