“Look, I have a lot of respect for GAO,” he said. “I look at it this way. The aid got there within the fiscal year … There are no investigations in the Ukraine. So if the process wasn’t handled as well as it should have been, then fair enough and we should look at that and make sure it is handled appropriately. Do I think this has any impact on impeachment? No I don’t.“

GAO, an independent nonpartisan government watchdog that responds to congressional requests, said the White House attempted to justify its decision not to notify Congress of the hold by claiming it was simply a “programmatic delay.” But GAO rejected that claim, saying Trump’s decision, carried out by the budget office, was a violation of the Impoundment Control Act, which requires notification to Congress of any such delay in an appropriation of funds.

“OMB’s assertions have no basis in law,” the GAO argues, referring to the White House Office of Management and Budget.

OMB spokeswoman Rachel Semmel pushed back on GAO’s conclusions.

“We disagree with GAO’s opinion,” Semmel said. “OMB uses its apportionment authority to ensure taxpayer dollars are properly spent consistent with the president’s priorities and with the law.”

The GAO report also states that OMB and the State Department “failed” to provide all of the information that was necessary for its investigation. That decision will likely fuel Democrats’ arguments in the Senate trial that Trump has attempted to obstruct Congress’ ability to investigate the Ukraine matter, and that he has been engaged in a “cover-up.” The second impeachment article alleges that Trump obstructed Congress when he ordered senior officials to refuse requests and subpoenas seeking testimony and documents.

“The nonpartisan Government Accountability Office has confirmed what congressional Democrats have understood all along: President Trump abused his power and broke the law by withholding security assistance to Ukraine,” House Appropriations Committee Chairwoman Nita Lowey (D-N.Y.) said in a statement.

Sen. Chris Van Hollen (D-Md.) requested GAO’s opinion in a letter last month, noting that several administration officials have raised concerns about whether the president’s decision violated federal budget law. The move prompted two White House budget officials to resign in part out of frustration. Senior officials at the Pentagon and State Department sought an explanation for the hold, but were ultimately unsuccessful.

Van Hollen sent the letter one week after the House voted to impeach Trump on Dec. 18, charging him with abuse of power and obstruction of Congress for allegedly using his office and federal resources to pressure Ukraine to investigate his political rivals — and then resisting the House’s investigation.

At issue in GAO’s legal opinion is how the Ukraine aid pause gels with the Impoundment Control Act of 1974, a law that sharply curbs the executive branch’s authority to alter congressionally appropriated funds.

Mark Sandy, a senior OMB civil servant, told House impeachment investigators last year that acting White House chief of staff Mick Mulvaney’s office informed OMB on July 12 that Trump planned to halt Ukraine’s aid without providing an explanation.

The administration released its hold on Sept. 11, just hours after a whistleblower complaint about the matter was circulating around the government, and after House committees began investigating Trump’s personal lawyer Rudy Giuliani and his efforts in Ukraine to spur Trump’s desired investigations.

The funds were set to expire at the end of the fiscal year on Sept. 30, and while the administration un-paused the money, millions of dollars never made it to Ukraine by the deadline.

House Democrats have said the Ukraine aid pause was part of a broader “pattern of abuse” by OMB, which has disregarded federal budget law and congressional spending authority.

House Budget Committee Chairman John Yarmuth (D-Ky.) is now drafting a bill aimed at keeping OMB in check, and Lowey is expected to sign on as a co-sponsor. Yarmuth said he expects to release the measure in mid-March.

John Bresnahan, Heather Caygle and Jennifer Scholtes contributed to this story.