Hagel warned of sharply deeper cuts to personnel, health care and weapons systems across his department, in order to put the brakes on spiraling costs and reshape the military for leaner budgets and new challenges. WASHINGTON (AP) - Defense Secretary Chuck Hagel put the Pentagon and Congress on notice Wednesday that he is considering fundamental changes to the size of the military's management and command structures, requiring sweeping and dramatic spending cuts that are likely to hit programs favored by lawmakers. Hagel said in a speech to the National Defense University at Fort McNair that escalating spending to maintain benefits, existing military structures and replacements for aging weapons programs are devouring funding needed for critical operations, training and equipment. The Pentagon, he said, must reevaluate the size of its management and military command structures, which continue to grow even as the overall force numbers decline. "I am concerned that despite pruning many major procurement programs over the past four years, the military's modernization strategy still depends on systems that are vastly more expensive and technologically risky than what were promised or budgeted for," Hagel said. Hagel also echoed other administration officials in calling North Korea's recent rhetoric a real, clear danger and threat to the U.S. and its Asia-Pacific allies and says America is doing all it can to defuse the situation. The U.S. has dispatched bombers, stealth fighters and ships to the region, in a show of force to deter any action by Pyongyang. And on Wednesday the Pentagon announced it will deploy a high altitude ballistic missile defense system to Guam in the coming weeks to strengthen the region's protections against the North Korean threat. The land-based system includes a truck-mounted launcher, tracking radar, interceptor missiles, and an integrated fire control system. But Hagel said he believes there is a path to peace on the troubled Korean peninsula, although it doesn't include making nuclear threats or taking provocative actions. While his speech focused on the need for the Pentagon to do much more to slash its spending, Hagel also made it clear that any budget cuts should not erode America's ability to be a force for global leadership. The Pentagon is already grappling with a $487 billion, 10-year reduction in projected spending as part of the budget law that Obama and congressional Republicans agreed to in August 2011. In addition to that, the military is now facing $41 billion in across-the-board cuts for this fiscal year that went into effect on March 1. The changes, he said, will involve "not just tweaking or chipping away at existing structures and practices but, where necessary, fashioning entirely new ones that are better suited to 21st century realities and challenges." In his first major address as Pentagon chief, Hagel embraced what is likely to be his major challenge in his term: shrinking the U.S. military despite persistent congressional mandates that slash funding but forbid the elimination of favored bases and programs that must be cut in order to achieve the required savings. Lawmakers have resisted Pentagon pleas for another round of base closures and to trim unwanted aircraft, or proposals to adjust military health care benefits as too politically risky. Closing bases and ending contracts can cost jobs in members' districts. "Much more hard work, difficult decisions and strategic prioritizing remains to be done," Hagel said, noting that "deep political and institutional obstacles to necessary reforms will need to be engaged and overcome." While both his predecessors launched reviews to identify hundreds of millions of dollars in savings, Hagel is taking over just as the automatic, across-the-board budget cuts are taking effect. In light of those reductions, he has already ordered a re-evaluation of the defense strategy that President Barack Obama announced early last year. That strategy called for a greater emphasis on the Asia-Pacific region, a continued focus on the Middle East and an increase in cybersecurity, missile defense and special operations forces. Asked specifically about the unpaid furlough days that civilians will be forced to take, Hagel acknowledged that the cuts will be painful but unavoidable. As many as 700,000 of the department's civilian workers will have to take 14 unpaid days off in the coming months to save about $2.5 billion. But he said officials are also looking at cutting layers of upper and middle management, including in the military commands, and are weighing whether the department has the right mix of military and civilians, and the correct balance of officers and enlisted troops. He also said he will ask Congress to look at ways to increase various fees, including those for health care and retirement programs. "We need to be steely-eyed and clear-headed in our analysis, and explore the full range of options for implementing our national security strategy," he said. But, despite the budget cuts, Hagel said the U.S. does not have the luxury of choosing to withdraw from the world. If we refuse to lead, something, someone will fill the vacuum. The next great power may not use its power as responsibly or judiciously as America has," he said. America has helped make a better world for all people with its power. A world where America does not lead is not the world I wish my children to inherit. Lolita C. Baldor can be followed on Twitter: https://twitter.com/lbaldor