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PHILADELPHIA -- Hours after creating a major political headache for his close friend and ally Hillary Clinton by suggesting she may support a controversial trade deal, Virginia Gov. Terry McAullife assured a group of union leaders Wednesday that she will never support the pact.

"Hillary is against TPP and she is always gonna stay against TPP. Let me be crystal clear about that," McAullife told a closed-door meeting of Democratic National Convention delegates who are members of the United Steelworker union, according to a video provided to NBC News by a source in the room. AFL-CIO President Richard Trumka sat by McAullife's side.

McAullife's pledge came as he tried to clean up a comment he made to Politico Tuesday night. "Yes," he said, Clinton could support the Trans Pacific Partnership trade deal with some changes.

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Clinton has spent the past year trying to convince skeptical progressives that she genuinely opposes the trade deal a dozen Pacific nations, which she praised as President Obama's secretary of state. So the comments from someone so close to the candidate created an immediate problem and sent campaign officials scrambling.

"I can be definitive. She is against it before the election and after the election," Clinton campaign chairman John Podesta said at a press conference Wednesday. "And she is not interested in renegotiating the TPP.

McAullife, who, like President Obama, supports the TPP, did not immediately walk back his remark.

Related: 5 Things to Know About the Trans Pacific Partnership

In an interview with NBC News' Andrea Mitchell Wednesday morning, McAullife left the door open for Clinton to one day support the deal, which is bitterly opposed by organized labor. "She would only go forward if changes she wants are implemented and everyone in agreement -- she is not going forward as it is today," he said.

But by Wednesday afternoon, McAullife apparently saw the need to be more definitive in stating Clinton's opposition to deal.

The Virginia governor chaired Clinton's 2008 presidential campaign and was given the honor of being the first speaker on the stage of the convention after Clinton was formally nominated as the party's candidate Tuesday night.

He will also choose a temporary replacement for Clinton's newly minted vice presidential pick, Virginia Sen. Tim Kaine, if she wins in November.

McAullife's comment created issues on both her right and left flanks. Clinton struggles with perceptions of being dishonest and taking policy positions for political reasons, so many Bernie Sanders supporters doubted the sincerity of Clinton's stance on the TPP.

Republican nominee Donald Trump, who also opposes the TPP, knocked Clinton on the McAullife quote as well. "Just like I have warned from the beginning, Crooked Hillary Clinton will betray you on the TPP," Trump said on Twitter.