Millions of dollars in military aid that’s at the heart of the ongoing impeachment inquiry still has not yet reached Ukraine, the Los Angeles Times reported.

More than $20 million of the $250 million the Pentagon is supposed to give to Ukraine remains in U.S. accounts, Department of Defense officials and Senate aides told the LA Times. It is unclear why a portion of that funding has not yet been disbursed.

“We still don’t have a clear understanding of why this is taking so long,” a Senate aide told the LA Times.

The delay in disbursing the funding comes as Republicans continue to claim that President Trump did not abuse his power when he held up hundreds of millions of dollars in funding from Ukraine because the money was released in September. But the withheld aid is at the center of the articles of impeachment the House Judiciary Committee is expected to vote out of committee Friday.