DES MOINES, Iowa (AP) — Sen. Chuck Grassley 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.

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.

Grassley says he doesn’t advocate journalists violating professional ethics.