Chief Justice John Roberts, who's presiding over President Donald Trump's Senate impeachment trial, refused to read aloud a question from GOP Sen. Rand Paul that named the Ukraine whistleblower.

Some Republicans, including Trump, have spent months pushing to reveal the whistleblower's identity, despite legal protections afforded to whistleblowers.

Democrats and some prominent Republicans have insisted that the whistleblower must be kept anonymous to protect the person from death threats and other forms of retaliation.

Paul privately expressed frustration on Wednesday night and said he'd continue pushing the issue, according to a CNN report.

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Chief Justice John Roberts, who's presiding over President Donald Trump's Senate impeachment trial, refused on Wednesday to read aloud a question from GOP Sen. Rand Paul that named the Ukraine whistleblower, multiple news outlets reported.

Some Republicans, including Trump, have spent months pushing to reveal the whistleblower's identity, even though federal law protects government whistleblowers from retaliation. Trump has repeatedly lashed out at the whistleblower, saying the person "hates Trump."

The whistleblower's identity has not been publicly verified, beyond that they are a member of the intelligence community. Democrats and some prominent Republicans have insisted that the whistleblower must be kept anonymous to protect the person from death threats and other forms of retaliation.

Paul privately expressed frustration on Wednesday night and said he'd continue pushing the issue, according to a CNN report.

"If I have to fight for recognition, I will," Paul reportedly told a GOP staffer.

On Wednesday, senators began a 16-hour period, over two days, of submitting written questions to the prosecution and the defense. Roberts reads those questions aloud.

The whistleblower's complaint, lodged in August, alleged that White House officials were "deeply disturbed" by a phone call during which Trump pressured the president of Ukraine to announce investigations that could benefit Trump politically.

The complaint also alleged that the White House subsequently engaged in a cover-up. You can read more details of the complaint and a timeline here.

Shona Ghosh contributed to this report.