WASHINGTON (CNN) -- Defense Secretary Robert Gates acknowledged Monday that proposed 2010 Pentagon budget cuts are likely to run into significant opposition on Capitol Hill, where politicians are concerned about preserving valuable defense contracts for their districts and states.
The new Pentagon budget proposal received a mixed reception from Republicans on Monday.
Gates said the new budget will reflect major changes in the "scope and significance" of the country's military priorities.
The proposed budget cuts several traditional big-ticket items while investing in programs designed to bolster the military's ability to fight terrorists and other extremist elements in multiple regions at the same time.
"This is a reform budget, reflecting lessons learned in Iraq and Afghanistan," Gates said. "There's no question that a lot of these decisions will be controversial."
He called on Congress to "rise above parochial interests and consider what is in the best interests of the nation as a whole." Watch more of Gates' comments »
Gates on Tuesday spoke to members of defense trade publications, Capitol Hill media and defense analysts from Washington think tanks, according to Pentagon officials.
The secretary also recorded an interview for the PBS show "The NewsHour with Jim Lehrer," to air Tuesday night. In that interview Gates tries to characterize his budget decisions in a friendlier tone than was portrayed by headlines such as Defense Daily's "Boeing Bloodied as Gates Proposes Slashing Missile Defense."
"It's really not as much about cuts; I know that there's a lot of focus on cuts because of four or five major programs. But it's really a rebalancing: How do we sustain the capability not only to fight the wars we are in, but also how we preserve the hedge to fight any future conflict," Gates said in the PBS interview, according to a transcript released by the network.
Rep. Ike Skelton, D-Missouri, chairman of the House Armed Services Committee, acknowledged that representatives have concerns about job losses in their home districts but said that ultimately, "the national interest overrides anything."
"The buck stops with us," he told CNN. "We still have a lot of hard work ahead of us."
Some of the budgetary changes include a stronger institutional commitment to the military's all-volunteer force, a decision to "rebalance" defense programs to better fight current and future conflicts, and "fundamental overhauls" of the military's procurement, acquisition and contracting process.
In what may be one of the most controversial parts of his proposed budget, Gates announced the cancellation or reduction of key elements of the Pentagon's missile defense system, including the installation of additional ground-based interceptor missiles in Alaska.
The proposed overall missile defense system budget was trimmed by $1.4 billion.
During Gates' announcement, a bipartisan group of senators released a letter urging him "not to allow deep cuts in U.S. missile defense programs that are critically important to protecting our homeland and our allies against the growing threat of ballistic missiles."
"The threat from ballistic missiles is significant and on the rise. [It] has been underscored by Iran and North Korea's recent missile tests," they said.
Among others, the letter was signed by both senators from Alaska: Republican Lisa Murkowski and Democrat Mark Begich.
While Gates was initially appointed Pentagon chief by former President George W. Bush, his overall budget received what appeared to be a mixed reception from congressional Republicans.
"Republicans appreciate Secretary Gates' effort to shape the Department of Defense so that we more effectively fight the wars our troops are engaged in today. However, we are concerned about the trade-offs involved in rebalancing the Department," New York Rep. John McHugh, the ranking Republican on the House Armed Services Committee, said in a written statement.
"It remains the Congress' responsibility to provide for the common defense," he warned.
However, Sen. John McCain, the former Republican presidential candidate, said Gates' budget "is a major step in the right direction."
"It has long been necessary to shift spending away from weapon systems plagued by scheduling and cost overruns to ones that strike the correct balance between the needs of our deployed forces and the requirements for meeting the emerging threats of tomorrow," he said.
"I believe Secretary Gates' decision is key to ensuring that the defense establishment closes the gap between the way it supports current operations and the way it prepares for future conventional threats."
Georgia Republicans, however, slammed President Obama for Gates' announcement about the phase-out of the F-22 Raptor, which is assembled in Cobb County, Georgia.
Rep. Tom Price, whose district includes the Raptor production facility, called the cut "outrageous" and said Obama's "priorities are deeply flawed." Georgia Sen. Saxby Chambliss said he was "disappointed" in the cuts and accused the administration of being "willing to sacrifice the lives of American military men and women for the sake of domestic programs."
Sen. Joe Lieberman, an independent from Connecticut, was also dismissive of the F-22 phase-out, although he said he generally supported Gates' moves to modernize the military. Some F-22 production takes place in Connecticut as well.
The proposed overall fiscal year 2010 Defense Department budget is almost $534 billion, or nearly $664 billion including the costs of the conflicts in Iraq and Afghanistan. The current Pentagon budget totals slightly more than $513 billion, or almost $655 billion including the Iraq and Afghanistan conflicts.
CNN's Ed Hornick, Adam Levine, Mike Mount and Alan Silverleib contributed to this report.