WASHINGTON - President Obama is planning to elevate a key national security deputy, Denis McDonough, to White House chief of staff, administration officials said Wednesday, making perhaps his closest foreign policy adviser the gatekeeper to the Oval Office.

Though Obama has not made a final decision, aides said, they expect an announcement early next week. McDonough would succeed Jacob Lew, another close aide whom Obama has nominated as Treasury secretary.

It would place a national security expert in a job that will require confronting a range of thorny domestic issues, including budget negotiations, gun violence and immigration.

"It's a new set of challenges for him," said former Sen. Tom Daschle, D-S.D., for whom McDonough worked before joining Obama in 2007, when he was a senator. But Daschle said McDonough had a qualification that trumped his policy background: "He has an extraordinarily close relationship with the president."

"What the president wants is a fairly tightly knit, cohesive team that he trusts," Daschle said, "rather than to bring in people who would have to learn anew his style and positions."

In that regard, McDonough, an intense, ascetic 43-year-old, may have no peer in the administration. A fervent Obama loyalist, McDonough has been immersed in every major foreign policy crisis and debate of the president's first term, enjoying a degree of access and level of trust that goes far beyond his age or job title.

Local roots

A native of Stillwater, Minn., McDonough grew up in a Catholic family of 11 children, one of whom became a priest. He played football at St. John's University in Minnesota, where he was known by the childhood nickname "Dude."

As a chief of staff, McDonough may lack the political pizazz of Rahm Emanuel, the backslapping bonhomie of William Daley or the budget-crunching acumen of Lew. But his friends say that he excels at precisely the kind of trains-run-on-time competence that Obama needs in a second term.

McDonough, his colleagues at the White House say, has a reputation for taking on problems no one else wants. He coordinated the administration's response to the deadly attack on the U.S. diplomatic mission in Benghazi, Libya, and its messy aftermath, for example.

He is also a relentless defender of Obama, as reporters on the receiving end of angry e-mails or phone calls from him can attest. His blasts were sometimes delivered during his nightly bike ride home to Takoma Park, Md., where he lives with his wife and three children. (After scrapes with motorists, he now mostly drives.)

As the principal deputy to the national security adviser, Thomas Donilon, McDonough has played a central role in assembling Obama's second-term national security team, building ties to candidates like Chuck Hagel, the nominee for secretary of defense. He is also close to John Brennan, Obama's chief counter-terrorism adviser, who was recently nominated to be director of the CIA.

A seat at the table

Along with Brennan, McDonough was one of a small circle of aides brought into the planning of the raid on Osama bin Laden's hideout in Pakistan. In a widely published photo of Obama and his staff watching the raid unfold in the Situation Room, McDonough had a seat at the table, next to Secretary of State Hillary Rodham Clinton.

He also convened a series of meetings to redefine the American mission in Afghanistan. That helped shape Obama's narrower ambitions for U.S. involvement, which were on display last week when he announced an accelerated plan to hand over responsibility for security to Afghan forces.

Much of McDonough's power derives from his entree to Obama. Colleagues say he has a keen sense for the president's instincts and preferences and no separate agenda.

"People throughout the foreign policy apparatus found out very quickly that when the national security adviser called, he might be calling for himself or for the president. But if Denis McDonough called, he was really calling for the president," said James Mann, the author of "The Obamians," a book about Obama's foreign policy team.

While McDonough has mostly exerted influence behind the scenes, he took a high-profile role in coordinating the U.S. response to the catastrophic earthquake in Haiti in early 2010 after Obama voiced frustration about the slow start of the effort.