WASHINGTON (AP) — A planned vote to move forward with Todd Blanche’s nomination for attorney general appeared in doubt Wednesday as a key Republican senator demanded more assurances from the Justice Department about the settlement of President Donald Trump’s lawsuit against the Internal Revenue Service.

GOP Sen. John Cornyn, a crucial swing vote, called off a scheduled Wednesday meeting with Blanche, who is already the acting attorney general. Cornyn told reporters that the Justice Department has not adequately addressed in writing his concerns about the settlement that afforded Trump and members of his family protection from tax audits.

The Senate Judiciary Committee has scheduled a vote for Thursday to advance Blanche’s nomination to the full Senate, but could be delayed if Blanche doesn’t win Cornyn’s support. Another Republican on the committee, Thom Tillis of North Carolina, has backed Cornyn’s position.

“They know what they need to do but they simply refuse to do it,” Cornyn said of the Justice Department.

At the center of the fight is the settlement of Trump’s $10 billion lawsuit against the IRS that included a deal to drop tax claims against the president and a now-scrapped plan to create a $1.776 billion “Anti-Weaponization Fund” to compensate people who believe they were wronged by the Justice Department. The Justice Department said in June that it was no longer moving forward with the “Anti-Weaponization Fund” amid bipartisan outrage but has said the audit immunity agreement remains in place.

Cornyn and Tillis have been pressing for further confirmation that the fund is dead despite repeated public assurances from Blanche, especially after Trump expressed continued support for the idea. Cornyn has also demanded clarification from the Justice Department on the scope of the tax immunity deal.

“We’re been trying to help them get to a conclusion here and they won’t let us. It’s befuddling to me,” Cornyn said.

A person familiar with the matter said the Justice Department provided Cornyn’s office with a written proposal seeking to address his concerns around the audit immunity agreement and the fund. The person spoke on the condition of anonymity to talk about sensitive discussions surrounding Blanche’s confirmation.

Alanna Durkin Richer And Joey Cappelletti, The Associated Press