A top Democrat in Congress on Wednesday challenged White House aide Stephen Miller to testify before the House Oversight and Reform Committee and defend the hardline immigration policies he has championed and, in some cases, engineered.

The offer by the chairman of the panel, Rep. Elijah Cummings, D-Md., appeared designed to appeal to the 33-year-old senior White House adviser's propensity for spirited debate. A video of Miller's contentious immigration showdown with CNN anchor Wolf Blitzer earlier in the year went viral.

The offer came days after Rep. Jerrold Nadler, D-N.Y., on Sunday said Miller, “who seems to be the boss of everybody on immigration,” should appear in front of Congress and try to explain the president's recently revived idea to send migrants from the border to sanctuary cities. Nadler told CNN that he learned from “whistleblowers” that Miller was behind the proposal.

The combative Miller is one of the White House's most conservative and influential voices in pushing other moves that Trump has taken to curb immigration, including the administration's travel ban on several Muslim-majority nations that was ultimately upheld by the Supreme Court.

WHITE HOUSE CONFIRMS PLAN TO SEND ILLEGAL IMMIGRANTS TO SANCTUARY CITIES IS UNDER ACTIVE THOROUGH REVIEW

The White House did not immediately respond to a request for comment. Past administrations have often refused to send White House aides to testify before Congress, though there have been exceptions.

Should such a session occur, it would be bound to ignite fireworks over an issue that has repeatedly produced heated clashes between Trump and congressional Democrats. Trump has made an immigration crackdown a cornerstone of his appeal to conservative voters, while Democrats — led by liberal and Hispanic lawmakers — have been just as adamant in opposing his moves.

"I understand that you may not want to submit yourself to rigorous questioning," Cummings said in his letter to Miller requesting his appearance.

"I want to make clear that I am inviting you to appear voluntarily," Cummings wrote. "I am offering you an opportunity to make your case to the committee and the American people about why you — and presumably President Trump — believe it is good policy for the Trump administration to take the actions it has."

Cummings cited the separation of migrant children from detained parents, a policy Trump withdrew under fire last year; Trump's threat to move detained migrants to "sanctuary cities," communities that limit cooperation with federal immigration authorities and that are mostly in Democratic areas; and the removal of top Homeland Security officials, including Secretary Kirstjen Nielsen.

Cummings said he wanted Miller to testify to his committee on May 1 and gave him until April 24 to respond.

Meanwhile, Senate Homeland Security Chairman Ron Johnson said he is working on legislation to help stem the flow of migrants at the U.S.-Mexico border.

Johnson, R-Wis., said he wants to toughen the initial standard for asylum seekers to "more than a probable chance" they'll experience violence or persecution in their home countries. Right now, if people can demonstrate "credible fear," they're allowed to stay in the U.S. as their cases progress.

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Johnson said in an interview that asylum cases must be adjudicated faster and that asylum seekers should be detained while they wait.

Johnson visited this week with migrants in Border Patrol custody on the southwestern border. He said most were seeking a better life and said that while he's sympathetic to their circumstances, that doesn't mean they should be granted asylum.

Fox News' Edmund DeMarche and The Associated Press contributed to this report.