WASHINGTON, D.C. — More than $35 million of the roughly $400 million in aid to Ukraine that President Donald Trump delayed, sparking the impeachment inquiry, has not been released to the country, according to a Pentagon spending document obtained by the Los Angeles Times.

Instead, the defense funding for Ukraine remains in U.S. accounts, according to the document. It’s not clear why the money hasn’t been released, and members of Congress are demanding answers.

The controversy began when Trump withheld the assistance package while urging new Ukrainian President Volodymyr Zelenskiy to conduct investigations of Trump’s political opponents. The White House lifted its hold on the money Sept. 11 after a whistleblower report emerged alleging a quid pro quo.

Lawmakers had days to save the aid from expiring at the end of the fiscal year in September. Knowing that the money couldn’t all be allocated in time, Congress gave the Pentagon an additional year to spend its share, which totaled about $250 million. The remainder of the package was to come primarily from the State Department.

Pentagon officials said then that the spending would be disbursed within weeks. But, $35.2 million —earmarked for grenade launchers, secure communications and naval combat craft —has not left the U.S. Treasury, according to lawmakers and the Pentagon document tracking spending.

Pentagon spokeswoman Lt. Col. Carla Gleason confirmed that $36 million had yet to be provided to Ukraine but declined to say why, instead reiterating that the aid would be obligated “over the next several weeks.”

The continued holdup of a portion of the assistance could undermine a key Republican argument throughout the impeachment inquiry. The president’s defenders have downplayed the effects of the delay in aid by noting that the funds were ultimately released without Ukraine committing to the investigations Trump wanted. A strategy memo circulated Monday night by Republican committee staff urged them to make that case in public hearings Tuesday.

Rep. Elise Stefanik, R-N.Y., said Tuesday during a hearing that two key facts have not changed throughout the inquiry: “Ukraine in fact received the aid and there was no investigation into the Bidens.”

White House press secretary Stephanie Grisham made the same point in dismissing the inquiry in a Fox News interview on Nov. 1. “The president did absolutely nothing wrong,” she said. “We released the transcript weeks ago for everybody to see. There was no quid pro quo. The Ukrainian government said they felt absolutely no pressure. Aid was eventually released to the Ukraine.”

Democratic lawmakers are demanding answers from the Pentagon as to why the aid for Ukraine has not yet been spent, nearly two months after the fiscal year ended Sept. 30.

Rep. John Garamendi, D-Calif., chairman of the House Armed Services Committee’s readiness subcommittee, said the Pentagon has not been responsive about the reason.

“We’ve raised the question and we have not received an answer,” Garamendi said. “We’re going to have to find out why.”

Senate Democrats on defense committees wrote to Secretary of Defense Mark Esper on Monday, emphasizing the importance of the aid reaching Ukraine in the aftermath of the controversy over the assistance.

“Speeding the delivery of this critical aid, which Congress specifically appropriated to improve the security of Ukraine, is important to affirm our commitment to Ukraine in the wake of the chaotic, undisciplined, and deeply concerning approach the administration has taken toward our important partner,” the letter said.