WASHINGTON (AP) — Attorney General William Barr used his final public appearance to undercut President Donald Trump on multiple fronts Monday, saying he saw no reason to appoint a special counsel to look into the president's claims about the 2020 election or to name one for the tax investigation of President-elect Joe Biden's son.

In the course of breaking with Trump on matters that have been consuming the president, Barr also reinforced the belief of federal officials that Russia was behind a massive hack of U.S. government agencies, not China as Trump had suggested.

Barr made the comments at a press conference to announce additional criminal charges in the bombing of Pan Am Flight 103, which killed 190 Americans, an issue he had worked on in his previous stint as attorney general in the early 1990s. He chose the announcement, in a case very personal and important to him, for his last public appearance, then took questions.

Barr said the Justice Department's existing investigation into Hunter Biden's financial dealings was "being handled responsibly and professionally."

"I have not seen a reason to appoint a special counsel and I have no plan to do so before I leave," he said. Nor for election fraud, he said.

Barr had been in lockstep with the president during much of his tenure as Trump's attorney general. But Trump, as he has done with many others in his inner circle, started criticizing Barr publicly. He was particularly angry that Barr didn't announce the existence of a two-year-old investigation of Hunter Biden.

And shortly before he announced his resignation, Barr told The Associated Press that he had seen no evidence of widespread voting fraud, despite Trump's claims to the contrary. Trump has continued to push baseless claims even after the Electoral College made Biden's victory formal Dec. 14.

A special counsel would make it more difficult for the incoming attorney general and president to close investigations begun under Trump. Doing so could lend a false legitimacy to baseless claims, particularly to the throngs of Trump supporters who believe the election was stolen because he keeps wrongly claiming it was.

Barr's statements Monday may make it easier for the acting attorney general who takes over, Jeffrey Rosen, to resist pressure from the White House to make such appointments.

In his 2019 confirmation hearing  for deputy attorney general, Rosen said he was willing to rebuff political pressure from the White House if necessary. He told legislators that criminal investigations should "proceed on the facts and the law" and prosecutions should be "free of improper political influences."

"If the appropriate answer is to say no to somebody, then I will say no," he said at the time.

Trump and his allies have filed roughly 50 lawsuits challenging election results and nearly all have been dismissed or dropped. He's also lost twice at the U.S. Supreme Court.

With no further tenable legal recourse, Trump has been fuming and peppering allies for options as he refuses to accept his loss.

Among those allies is Rudy Giuliani, who during a meeting Friday pushed Trump to seize voting machines in his hunt for evidence of fraud. The Homeland Security Department made clear, however, that it had no authority to do so. It is also unclear what that would accomplish.

For his part, Barr said he saw no reason to seize them. Earlier this month, Barr also told the AP that the Justice Department and Homeland Security had looked into the claims "that machines were programmed essentially to skew the election results" and ultimately concluded that "so far, we haven't seen anything to substantiate that."

Trump has consulted on special counsels with White House chief of staff Mark Meadows, White House counsel Pat Cipollone and outside allies, according to several Trump administration officials and Republicans close to the White House who spoke to The Associated Press on condition of anonymity because they weren't authorized discuss the matter publicly.

Trump was interested both in a counsel to investigate the younger Biden's tax dealings and a second to look into election fraud. He even floated the idea of naming attorney Sidney Powell as the counsel — though Powell was booted from Trump's legal team after she made a series of increasingly wild conspiratorial claims about the election.

Federal law requires that an attorney general appoint any special counsels.

Barr also said Monday the hack of U.S. government agencies "certainly appears to be the Russians."

In implicating the Russians, Barr was siding with the widely held belief within the U.S. government and the cybersecurity community that Russian hackers were responsible for breaches at multiple government agencies, including the Treasury and Commerce departments.

Hours after Secretary of State Mike Pompeo said in a radio interview that Russia was "pretty clearly" behind the hacks, Trump sought to undercut that message and play down the severity of the attack.

He tweeted that the "Cyber Hack is far greater in the Fake News Media than in actuality." He also said China could be responsible even though no credible evidence has emerged to suggest anyone other than Russia might be to blame.

Barr's comments came on the 32nd anniversary of the Pan Am explosion over Lockerbie, Scotland, that killed 259 people in the air and 11 on the ground.

The Justice Department announced its case against the accused bombmaker, Abu Agela Masud Kheir Al-Marimi, who admitted in an interview with Libyan officials several years ago that he had built the bomb and worked with two other defendants to carry out the attack, Barr said.

Calling the news conference to announce the charges underscored Barr's attachment to that case. He had announced an earlier set of charges against two other Libyan intelligence officials in his capacity as acting attorney general nearly 30 years ago, vowing that the investigation would continue.

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Associated Press writer Eric Tucker contributed to this report.