President Barack Obama will appoint a White House budget officer to the be the new acting Internal Revenue Service commissioner, an announcement made following a fresh declaration from the president that he knew nothing about the inspector general’s report detailing improper IRS actions until it was leaked.

After announcing the resignation of acting IRS Director Steven Miller on Wednesday evening, the president emerged Thursday afternoon to answer questions from the press about actions taken by IRS employees to single out conservative and Tea Party advocacy groups for extra scrutiny in their applications for nonprofit status.

"I can assure you that I certainly did not know anything about the I.G. report before the I.G. report had been leaked ... through the press," said Obama. "Typically, the I.G. reports are not supposed to be widely distributed or shared. They tend to be, you know, a process that everybody's trying to protect the integrity of. But, what I'm absolutely certain of is that the actions that were described in that I.G. report are unacceptable."

After what's arguably been the president's toughest political week since winning reelection to a second term, Obama named a new head of the IRS and announced a new push for increased security for diplomats abroad. NBC's Chuck Todd reports.

The president declined to endorse appointing an independent counsel to investigate the controversy -- an idea that some Republicans have demanded. The criminal investigation initiated by the Justice Department, combined with the administration's efforts to cooperate with lawmakers in their investigations, Obama argued, should be sufficient.

"I think it's going to be sufficient for us to be working with Congress," he said.

Just hours after that event, the White House said that Daniel Werfel, current controller of the Office of Management and Budget, would be named acting IRS chief, effective May 22.

In a press release, Obama said, "The American people deserve to have the utmost confidence and trust in their government, and as we work to get to the bottom of what happened and restore confidence in the IRS, Danny has the experience and management ability necessary to lead the agency at this important time."

Later Thursday, NBC News confirmed that a second top Internal Revenue Service official has announced plans to leave the agency. An internal IRS memo says that Joseph Grant, commissioner of the agency's tax exempt and government entities division, will retire June 3.

Of the three controversies that dominated Washington this week, the IRS issue has proven the most politically noxious for Obama.

The White House has also been besieged by new questions about its response to last year's terrorist attack against a diplomatic installation in Benghazi, Libya, along with revelations that the Justice Department had monitored Associated Press journalists' phone records.

The IRS and AP cases have been particularly thorny politically for one of Obama's top allies in the cabinet, Attorney General Eric Holder, who on Wednesday faced grilling on Capitol Hill for his role in both controversies. Republicans renewed some of their longstanding demands that Holder resign his position, demands which the president rejected on Thursday.

"I have complete confidence in Eric Holder as attorney general," Obama said.

President Barack Obama talks about the inspector general's report relating to alleged targeting of political groups by the IRS.

After weathering blistering criticism from Republicans, the administration has begun trying to craft its response to all three issues.

To that end, Obama on Thursday announced new measures meant to enhance security for U.S. diplomatic postings abroad as part of the administration's continued reaction to the Benghazi incident.

"I am intent on making sure we do everything we can to prevent another tragedy like this from happening again," Obama said at the White House.

His remarks come amid intensified efforts by Republican members of Congress to probe the Obama administration's reaction to the Sept. 11, 2012 attacks, which left four Americans dead, including U.S. ambassador Christopher Stevens.

The administration has sought to turn the narrative on that matter in its favor beginning Wednesday, when it released emails documenting how the administration crafted its first public responses to the attack.

Obama called on members of Congress in both parties to "come together" and work to authorize legislation to help fortify embassies and other diplomatic installations as a tribute to the deceased in Benghazi.

Jason Reed / Reuters President Barack Obamaand Turkish Prime Minister Recep Tayyip Erdogan arrive for a joint news conference in the White House Rose Garden in Washington, May 16, 2013.

Still, the controversy involving the AP helped prompt the administration to renew its efforts to have Congress authorize a federal shield law that would protect journalists from having to disclose confidential details of their work in court.

"To the extent that this case has prompted renewed interest with respect to how do we strike that balance properly, I think that now's the time for us to revisit that legislation," Obama said. "I think that's a worthy conversation to have."

Whether any of Obama's actions will placate Republicans, who are eager to use these controversies to gain political traction and slow or halt the president's second-term agenda, remains to be seen.

Lawmakers in both parties plan a series of high-profile hearings, beginning on Friday, on each of the controversies. And Republicans in particular have been eager to make political hay of the administration's recent missteps.

Speaking before the president this morning on Capitol Hill, House Speaker John Boehner, R-Ohio, said the controversies were a mark of “remarkable arrogance” by the president and his administration, though Boehner said that the Republican-controlled House was still primarily focused on the business of legislating.

NBC's Peter Alexander and Kelly O'Donnell contributed to this report.

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