(CNN) President Donald Trump's nominee to lead the Bureau of Alcohol, Tobacco, Firearms and Explosives is facing stiff opposition from some Senate conservatives, leaving Chuck Canterbury's confirmation in jeopardy after a Senate Judiciary Committee vote on the nomination was delayed last week.

In this January 2017 file photo, Chuck Canterbury National president of the Fraternal Order of Police speaks at the Senate Judiciary Committee hearing on nomination of Sen Jeff Sessions (R-AL) for attorney general on Capitol Hill in Washington, DC.

Conn Carroll, a spokesman for Republican Sen. Mike Lee of Utah, told CNN in a statement that Lee has concerns about Canterbury's nomination.

"Sen. Lee does have concerns about Canterbury's Second Amendment views and is pleased his nomination has been delayed," Carroll said.

Canterbury faced tough questions from both Republican and Democratic lawmakers in July, including from Republican Sen. John Kennedy of Louisiana, who told Canterbury he was being "evasive" and pressed him to reveal his personal views on the second amendment. Ultimately, Canterbury told Kennedy, "I don't personally support any more restrictions than are currently in the law."

Criticism within gun rights groups of Canterbury had been growing recently as his nomination and talks of a gun package progressed concurrently on Capitol Hill , though no significant gun control package has yet to substantially materialize this fall.

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