Office of Personnel Management director Katherine Archuleta has resigned just a day after revelations that 21.5 million Americans had their personal data compromised in a massive hack of the federal government's computer system.

OMB's U.S. Chief Performance Officer and Deputy Director for Management Beth Cobert will serve as acting director until President Obama appoints a permanent replacement.

Her decision to step down came after several top House Republicans, including Speaker John Boehner, R-Ohio, called for her resignation.

"This morning, I offered, and the President accepted, my resignation as the Director of the Office of Personnel Management," she said in her resignation statement.

"I conveyed to the president that I believe it is best for me to step aside and allow new leadership to step in, enabling the agency to move beyond the current challenges and allowing the employees at OPM to continue their important work," he added.

Less than a day earlier, when Archuleta was talking about the personal data stolen from more than 22 million people through OPM's computers, she brushed off questions about whether she would be leaving her job. "I am committed to the work that I am doing at OPM," Archuleta said.

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While Archuleta said leaving was her decision, the White House indicated that there was likely pressure on her to resign.

"What the president thinks is that it's quite clear that new leadership with a set of skills and experiences that are unique to the urgent challenges that OPM faces [is] badly needed," White House spokesman Josh Earnest said.

Archuleta has been blasted by both Republicans and Democrats for failing to heed several years' worth of warnings about the possibility of a cyberattack. Still, Archuleta said leading OPM was "the highlight of my career."

She also said she's "proud of the work we have done to develop the REDI initiative and our IT strategic plan," and said she has "complete confidence" in the remaining staff at OPM to carry out the agency's mission of recruiting and training federal workers.

House Republicans said Archuleta was making the right decision after such a major breach.

"This is the absolute right call," Rep. Jason Chaffetz, a Utah Republican who chairs the House Oversight and Government Reform committee, said in a statement. "OPM needs a competent, technically savvy leader to manage the biggest cybersecurity crisis in this nation's history."

OPM's inspector general has been warning about security lapses at the agency for years and security should have been strengthened much sooner, Chaffetz said.

"I appreciate the president doing what's best now," he said. "In the future, positions of this magnitude should be awarded on merit and not out of patronage to political operatives."

Archuleta was national political director for Obama's 2012 re-election campaign, and Republicans have said putting her in charge of OPM was much more of a political favor instead of a move to find a qualified person to lead the agency.