WASHINGTON ― U.S. Sen. Joe Manchin said Tuesday that he hasn’t made a decision on Colin Kahl’s nomination after speaking with Defense Secretary Lloyd Austin, leaving President Joe Biden’s pick for undersecretary of defense for policy stuck in limbo.

“I have reached out to Republicans who he’s worked with and who he’s worked under. I wanted to get everybody’s input. So, I’m gathering all that information. I have not made a final decision,” Manchin, D-W.Va., told Fox News’ Bret Baier.

Manchin’s vote on the Senate Armed Services Committee may be pivotal to advancing Kahl’s nomination to the Senate floor. Several Republicans have said they would oppose Kahl, citing what they view as partisan social media activity and his vocal support for the 2015 Iran nuclear deal ― and if panel Republicans vote as a bloc, Kahl will need Democrats to unify behind him.

After Manchin joined Republican opposition to Neera Tanden as the nominee for Biden’s budget director, citing her past tweets criticizing politicians across the spectrum, the White House dropped Tanden’s nomination. Manchin was also one of four Democrats to vote against the Iran nuclear deal.

Austin, meanwhile, has urged the Senate to hold a vote to confirm Kahl, according to Pentagon Spokesman John Kirby. Kahl was previously a senior adviser to President Barack Obama and then-Vice President Biden, as well as deputy assistant secretary of defense for the Middle East from 2009 to 2011.

On Tuesday, Manchin said Kahl’s “tweeting is nowhere near what Neera Tanden’s was.” Manchin expressed mixed feelings about one 2019 tweet from Kahl ― after President Donald Trump abruptly withdrew U.S. troops from Syria, that Republicans defending him “debase themselves at the alter of Trump - they are the party of ethnic cleansing.”

To help himself decide, Manchin said he had spoken with Kahl, Austin and former Defense Secretary Bob Gates, a Republican.

“These are good people, and you want to get all the inputs you can,” Manchin said. “I want to know the demeanor of that person. I want to know the temperance of that person. I want to get the feel of who that person is.”

During Kahl’s SASC confirmation hearing last week, he faced sharp questions from Republicans and apologized for his “sometimes disrespectful” remarks on social media, pledging to serve in a nonpartisan fashion if confirmed.

On Tuesday, West Virginia Republican Sen. Shelly Moore Capito became the first Republican outside the SASC to come out against Kahl, retweeting a Wall Street Journal editorial opposed to his confirmation.

“The world’s largest state sponsor of terrorism does not deserve to be coddled, and the disastrous Iran nuclear deal should be left in the past,” she said, adding: “We need a strong, not soft, stance when it comes to Iran. Colin Kahl is the wrong choice for such an integral role at the Pentagon.”