President Trump’s picks for attorney general and U.N. ambassador have run into immediate opposition from Democrats -- suggesting both nominees could face tough confirmation hearings.

Trump announced Friday morning that he plans to nominate William Barr, the George H.W. Bush-era leader of the Justice Department, as his next attorney general to replace former AG Jeff Sessions. Fox News is told Trump liked the respect Barr commands and the fact that he has earned bipartisan support in the past. If confirmed, he would replace Matthew Whitaker, the former Sessions chief of staff who took over as acting attorney general last month.

He also announced that he has chosen State Department spokeswoman Heather Nauert to succeed outgoing U.N. Ambassador Nikki Haley, who is stepping down from her role in January.

But it is unclear whether either Nauert or Barr will garner bipartisan support given the politically charged environment on the Hill. Barr in particular drew concerned statements from Democrats -- particularly in the shadow of FBI Special Counsel Robert Mueller’s ongoing Russia probe. House Democratic Leader Nancy Pelosi, D-Calif., called Barr’s pick “deeply concerning.”

“Barr has spent the past two years auditioning for this job by stoking partisan attacks on our nation’s law enforcement community, and encouraging the President to use the Justice Department as a political weapon to pursue his rivals and undermine investigations into Trump and his family’s scandals,” she said, before saying Barr’s selection was “the latest in the President’s pattern of installing partisan hacks in the highest reaches of our government who will happily do his bidding.”

Sen. Dianne Feinstein, D-Calif., expressed concern about Barr’s “expansive views of executive power and partisan statements about pardons, the Mueller investigation and Hillary Clinton.”

TRUMP TAPS WILLIAM BARR FOR ATTORNEY GENERAL, HEATHER NAUERT FOR UN AMBASSADOR

She said, “Barr must commit to supporting Special Counsel Mueller’s investigation and allowing him to follow the facts. He must also commit to resisting political pressure placed on the Justice Department. I look forward to receiving his answers to questions in these and other areas during the confirmation process.”

Senate Minority Leader Chuck Schumer, D-N.Y., appeared to predict a lengthy confirmation hearing, issuing a laundry list of issues Democrats want to discuss with Barr.

“Once Mr. Barr’s nomination is formally sent to the Senate, we will carefully and thoroughly examine Mr. Barr’s record and probe his views on many subjects, including but not limited to his views on the independence of the position, executive authority, LGBTQ rights, civil rights, voting rights, protections for people with pre-existing conditions, the environment, consumer protection and anti-trust, and others,” he said.

The scrutiny on Barr comes as Democrats also rail against Whitaker in his acting AG role. Republicans, though, cheered Trump's choice of Barr.

Senate Judiciary Chairman Chuck Grassley, R-Iowa, said in a statement that Barr is “a talented, well-respected lawyer who has been committed to public service over the course of his long career.”

“His compelling credentials and experience, serving at the highest levels in both government—including as a former attorney general under President George H.W. Bush—and in the private sector, make him more than well-qualified to lead the Department of Justice again,” Grassley said in a statement.

Nauert’s expected nomination drew less fire from Democrats, but comments by Sen. Chris Murphy, D-Conn., on Thursday -- before the pick was formally announced -- indicated that Democrats were likely to push a narrative that Nauert, who is the State Department spokeswoman, is “not qualified.” Murphy cited Nauert’s past experience as a Fox News journalist -- where she also was an anchor on “Fox & Friends.”

“She is clearly not qualified for this job, but these days it seems that the most important qualification is that you show up on Donald Trump’s TV screen, and if you’re successful in that endeavor, then you seem to be a top candidate to get a whole bunch of top positions in the U.S. government,” he said on CNN.

However, Nauert’s pick received support from Republicans, as well as some international allies. House Speaker Paul Ryan, R-Wis., described Nauert as an “excellent selection” by Trump.

“As one of the United States’ strongest voices on the global stage, Heather will seamlessly transition to the country’s top diplomat at the U.N.,” he said.

Israeli Ambassador to the U.N. Danny Danon said Nauert has "stood by the State of Israel in her previous positions, and I have no doubt that the cooperation between our two countries will continue to strengthen as ambassador to the U.N.,"

While the Democratic resistance to both Barr and Nauert could be an obstacle, Republicans can confirm nominees without Democratic support provided they hold together. The GOP's slim Senate majority will increase to 53 seats in January.

Fox News' John Roberts and Mike Emanuel contributed to this report.