(CNN) - A Senate committee Wednesday delayed a vote on the nomination of Ron Vitiello to lead Immigration and Customs Enforcement amid criticism of some personal tweets and the Trump administration's policies on family separation.
Homeland Security Chairman Ron Johnson, R-Wisconsin, said "serious issues" have been raised and need to be answered.
"We are going to continue to do some due diligence. The unions have raised some serious issues which we're looking into and I think that's appropriate," Johnson said Wednesday. "So I'm not sure when we may take a vote on that. We're getting very quick responses and I seem to think some very good responses from Mr. Vitiello and from [the Department of Homeland Security] on some of the issues raised. We may be able to move that quickly."
Vitiello has been leading ICE in an acting capacity since the end of June. He previously was chief of the US Border Patrol and acting deputy commissioner of Customs and Border Protection.
At Vitiello's confirmation hearing on Nov. 15, he faced some criticism for refusing to rule out potential future family separations, as well as controversy over personal tweets and an immigration event he had attended.
In a letter to the committee after his hearing, the head of the ICE union Chris Crane raised concerns about Vitiello's decision to prohibit union officials from performing agency duties, the management of the protests at the ICE Portland office -- which took place before Vitiello assumed his acting role -- and his personal tweets.
Crane asked that Vitiello respond as to whether he had ever been disciplined for tweets referencing then-presidential candidate Donald Trump and Dennis the Menace, as well as a tweet suggesting the Democratic Party be renamed the "Neo-Klanist" party.
Michigan Democrat Gary Peters asked about the 2012 tweet, in which Vitiello "suggested that the Democratic Party should be renamed the 'liberalcratic party' or the "Neo-Klanist party.' "
Vitiello acknowledged "it was a mistake" and says "he was trying to make a joke," adding that he thought it was a direct message.
He called it "a momentary lapse of judgment."
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