The heads of the Senate judiciary committee are writing a letter to Donald Trump Jr. Thursday requesting that he testify before the committee, Chairman Chuck Grassley told CNN.

Grassley, R-Iowa, previewed his intentions Wednesday when he told reporters that he wanted former Trump campaign chairman Paul Manafort to testify before the committee as early as next week, following revelations related to Trump Jr.'s email exchange with a Russian lawyer regarding potentially damaging information against Hillary Clinton.

Grassley's comments also come after the top Democrat on the committee, California Sen. Dianne Feinstein told CNN Thursday she wanted Trump Jr. to go before the committee as early as next week.

Trump Jr. on Tuesday morning posted a series of emails between himself and Rob Goldstone, a music publicist who contacted Trump Jr. and told him about an opportunity to receive potentially damaging information about Clinton as part of a Russian government effort to help his father's campaign. That email led to the June 9, 2016 meeting, at which Trump Jr. later said no meaningful information was provided.

On Tuesday, Trump Jr. told Fox News' Sean Hannity: "In retrospect, I probably would have done things a little differently," but added that the meeting came before Russian involvement becoming a major story during the campaign season.