The chairman of the Senate Judiciary Committee on Thursday said he wants Donald Trump Jr. to testify before the committee, following emails showing Trump Jr. met with a Russian lawyer he believed would provide dirt on Hillary Clinton as part of a Russian government effort to aide his father’s campaign.

What would you want to ask him or learn about?” CNN’s Manu Raju asked Grassley Thursday. “Why is this under your committee’s jurisdiction?”

“Well, very much because our oversight of the Justice Department,” Grassley said. “And I think it’s just — it’s raised a lot of questions, but the real way that I feel comfortable inviting him is ever since I’ve — ever since President Trump was elected, it seems like every conversation that has come from somebody in the family where there’s been some sort of issue, they’ve seemed always to be very, very open, and I just think that he would welcome the opportunity to say whatever he wants to say.”

“Would you subpoena him” if he did not agree to testify voluntarily? Raju asked.

“Let’s wait and see what he does for, from our letter,” Grassley responded before walking away.

A spokesman for the Judiciary Committee did not respond to TPM’s requests for comment on the details of Grassley’s request to Trump Jr.

In emails Trump Jr. released just before a New York Times report on them Tuesday, the then-candidate’s son is seen responding enthusiastically to the promise of dirt on Hillary Clinton as part of a Russian government effort to aide his father’s 2016 presidential campaign.

After Trump Jr. published the emails, several senators on both sides of the aisle in the Senate Intelligence and Judiciary committees said the Trump scion should testify about the resulting June 9 meeting between him, Jared Kushner and Paul Manafort, and the Russian lawyer Natalia Veselnitskaya.

On Wednesday, the Des Moines Register reported, Grassley told Iowa reporters on a press call that he intended to bring Manafort in front of the committee to answer questions.

This post has been updated.