Sen. Chuck Grassley, the president pro tempore of the United States Senate, doesn’t agree with calls from President Donald Trump and other Republicans to reveal the identity of the whistleblower who first reported concerns about Trump’s dealings with the Ukrainian president.

Grassley, who wrote significant portions of federal whistleblower laws, says they ensure anonymity for whistleblowers and should be followed.

Haaretz Weekly Ep. 47 0:00 -- : -- 15 Skip 15 seconds backwards Play audio 15 Skip 15 seconds ahead 1 X Change playback rate from 1 to 1 Mute audio

Grassley told reporters in a call Wednesday that it’s important not to reveal the identity of intelligence agency whistleblowers because it could endanger them.

He says the whistleblower is less important now that documents have been released of the call that led the U.S. House to begin an impeachment inquiry into whether Trump sought favors from the Ukrainian president that would help Trump’s re-election campaign.

Trump and Sen. Rand Paul called on reporters to release the whistleblower’s identity this week.

Donald Trump Jr. tweeted Wednesday the alleged name of the whistleblower whose anonymous complaint led to the impeachment inquiry into U.S. President Donald Trump.

The president's son alleged that they "worked closely with anti-Trump dossier hoaxer," adding a link to an article in the far-right news website Breitbart.

Grassley says he doesn’t advocate journalists violating professional ethics (Haaretz will not publish the name of the alleged whistleblower).

After widespread backlash following the tweet, Trump Jr. defended his move writing: "I love the outrage about me tweeting an article about the 'alleged' whistleblower... also good to know you have other sources confirming. Those thinking I coordinated with The White House to tweet out a@BreitbartNews article haven’t been watching my feed much. Didn’t happen!"

On Sunday the U.S. official had offered to communicate directly with Republicans on the intelligence committee leading the inquiry. The action was in response to Republican efforts, led by Trump, to unmask the whistleblower, a member of the U.S. intelligence community whose identity has not been released, their lawyer Mark Zaid said. Republicans have "sought to expose our client's identity which could jeopardize their safety, as well as that of their family," Zaid wrote on Twitter.

News of the offer came as Trump called on the whistleblower to come forward, in a stark departure from norms in such cases.

"The whistleblower should be revealed, because the whistleblower gave a false story," Trump said on the White House lawn Sunday, while calling him an "Obama guy" and a "fraud."

Reuters and Associated Press contributed to this story