CHICAGO (AP) — Deputy Attorney General Rod Rosenstein came to Chicago to speak on Thursday, but steered clear of discussing a conservative Republican effort to impeach him or President Donald Trump's calls to halt the investigation into Russian election interference that Rosenstein is overseeing.

In a 20-minute speech followed by a 10-minute question-and-answer session at the American Bar Association's annual meeting, Rosenstein barely mentioned Trump, and when he did it was to praise the president for the leadership team he installed at the Justice Department.

But Rosenstein said it was the duty of government lawyers and all attorneys to be "guardians of the rule of law" and he made it clear repeatedly that he will resist political pressure to interfere in any way with special prosecutor Robert Mueller's investigation.

The Department of Justice, he said must "never be a partisan actor" and has e a duty to "insulate investigations from the real and appearance of political influence..."

Further, amid the talk from conservative lawmakers and pundits about the lack of evidence that the president colluded with the Russians, Rosenstein said that "the rule of law requires us to reserve judgment until we have heard from all the parties and considered all the evidence."

And, he said, "we need to hold people accountable when they break the rules."

Rosenstein in his speech took pains to put what is happening now in historical context, mentioning Abraham Lincoln, Benjamin Franklin, John Adams and others. He made a point of quoting respected attorneys general who held their jobs two years or less.

"Just saying," he said, to laughter of the audience that showed its appreciation of Rosenstein's public service with two standing ovations.

Sworn in in April of last year, Rosenstein began overseeing Mueller's probe when Attorney General Jeff Sessions recused himself following reports of a meeting he had with a Russian ambassador.

As the investigation continued, a furious Trump has repeatedly criticized Sessions for recusing himself, criticized the investigation and as recently as this week tweeted that Sessions must put an immediate stop to what he called a "Rigged Witch Hunt." At the same time, a group of 11 conservative Republican lawmakers have launched an effort to have Rosenstein impeached.

That effort has stalled, with House Speaker Paul Ryan speaking out against impeaching Rosenstein and Sessions voicing his support for his deputy.