President Barack Obama will sharply cut ships, aircraft, and troops as part of a major reduction of U.S. military forces that will face even steeper downsizing in 2016, Defense Secretary Chuck Hagel announced on Monday.

The defense cuts, to be announced formally in the president’s budget proposal next month, would reduce U.S. ground forces to their lowest level since World War II at a time when world threats are increasing.

The defense secretary outlined the dramatic reductions in a briefing for reporters at the Pentagon. They include significant cuts in Navy shipbuilding and Air Force aircraft purchases, and a 20 percent reduction in Army ground forces.

Several new weapons systems will be slashed and older weapons retired.

The military cutbacks have been a central feature of Obama’s policies since 2009. According to former Defense Secretary Robert Gates, in his recently published book Duty, since entering office, the president has worked to cut U.S. defenses in order to use the funds for domestic programs.

Hagel said the defense reductions will pose new national security risks for the United States in the future. They also have forced the Pentagon to face the prospect of losing America’s position as the most dominant military power in the world.

The force reductions when combined with the spread of advanced weapons around the world signal "we are entering an era where American dominance on the seas, in the skies, and in space can no longer be taken for granted," the defense secretary said.

The announced cuts for the fiscal 2015 budget and future years follow an earlier cut of $487 billion in defense spending over 10 years and automatic spending cuts imposed on the Pentagon by the Budget Control Act. Those cuts, known as sequestration, included $37 billion last year and involve an additional $75 billion in cuts in 2014 and 2015.

After the recent budget agreement in Congress, additional sequestration cuts were put on hold until 2016, when new cuts amounting to $600 billion over a total of 10 years will be reimposed.

Congress must approve the new cuts.

Hagel said the spending cuts are forcing the Pentagon to "adapt, innovate, and make difficult decisions to ensure that our military remains ready and capable, maintaining its technological edge over all potential adversaries."

"However, as a consequence of large budget cuts, our future force will assume additional risk in certain areas," he said.

The military impact will include diminished training and maintenance and increased stress on forces. It also will result in "diminishing our global readiness even as we sustain a heightened alert posture in regions like the Middle East and North Africa," Hagel said.

The cuts will also increase the "risk of uncertainty in a dynamic and increasingly dangerous security environment," he added.

In particular, advanced weapons of "other powers" will make it more difficult for the military in dealing with those threats, including anti-air and anti-ship weapons, he said.

China confirmed last month that it conducted the first flight test of an ultra-high-speed maneuvering vehicle that can be used to deliver nuclear warheads and to defeat U.S. strategic missile defenses.

Hagel said the cuts also would reduce the ability of U.S. military forces to conduct more than one major military conflict in the world at the same time, something that could potentially trigger an outbreak of global conflict.

Still, Hagel said the Obama budget would give the U.S. military the ability to defeat any aggressor.

However, managing the risks will be more difficult after 2016, when further deep cuts are scheduled to take effect.

Hagel outlined the major cuts in forces for the fiscal 2015 budget, scheduled for release March 5.

The Army will be cut from its current level of 520,000 active duty troops to between 440,000 and 450,000 troops. That size is the smallest the service has been since 1940, prior to World War II. The Army at that time had 267,767 troops. In 2016, the troop level could be reduced further to 420,000 troops.

Hagel said the cuts would make the Army "highly ready and capable" and "able to dominate any opponent across the full spectrum of operations."

The current force is "larger than we can afford to modernize and keep ready," he said.

The defense secretary also announced he is killing the Army’s Ground Combat Vehicle program, a $28 billion program to replace armored vehicles currently in use.

"While this smaller capacity entails some added risk if we execute extended or simultaneous ground operations our analysis showed that this force would be capable of decisively defeating aggression in one major combat theater, as it must be, while also defending the homeland and supporting air and naval forces engaged in another theater against an adversary," Hagel said in defending the Army drawdown.

Army National Guard and Reserve forces also will be cut from 560,000 troops to 530,000 troops.

The Air Force will reduce the number of tactical air squadrons, including the elimination of the tank-busting, close-air support A-10 jet. All U-2 reconnaissance aircraft will be retired in favor of the unmanned Global Hawk drone, and armed Predator unmanned drones will be cut from a planned force of 65 non-stop air patrols to a planned force of 55 combat patrols. The more advanced Reaper drone will be purchased and eventually replace the Predator.

However, should sequestration resume at projected levels in 2016, the Air Force will cut 80 additional aircraft, including the entire KC-10 aerial refueling tanker fleet, additional Global Hawks and scale back purchases of the F-35 Joint Strike Fighter, a jet plagued with cost overruns. Predator and Reaper purchases also will decline after 2016.

For the Navy, 11 aircraft carrier strike groups will be kept but the USS George Washington will be retired in 2016, leaving 10 carrier groups.

Eleven warships—half of the Navy’s cruiser fleet—will be taken offline or placed in a reduced operating status while they are upgraded.

Navy ships purchases will include two destroyers and two attack submarines per year along with one additional floating staging base.

Hagel said Navy plans for Littoral Combat Ships, designed for mine-sweeping and anti-submarine warfare near coasts, are being limited to 32 ships, amid concerns the warships would not survive against advanced Chinese weaponry.

The Navy will examine producing an alternative small warship similar to a frigate instead of more Littoral Combat ships.

Six warships would be mothballed in 2016 and the rate of building new destroyers would be slowed, he said.

Marine Corps cuts will include further planned reductions from the current level of 190,000 Marines to 182,000 Marines, with a further cut to 175,000 after 2016.

Hagel revealed that the defense cuts for the first time in decades will force the military to consider adopting asymmetric, high-technology weapons and capabilities in order to prevail in future conflicts against enemies in the future with advanced war fighting skills.

Ostensibly, the force reductions are being made as the war in Afghanistan winds down and the administration is seeking to reposition forces to the Asia Pacific to deal with China’s growing military buildup and increasing assertiveness in making maritime claims over international waters.

The administration’s defense focus for the future is on "new technologies, new centers of power, and a world that is growing more volatile, more unpredictable, and in some instances more threatening to the United States," Hagel said, adding that current defense spending limits have forced the military to "face significant readiness and modernization challenges next year."

To deal with the military readiness shortfalls, Obama has proposed adding $26 billion to defense for fiscal 2015 as part of what is called "Opportunity Growth and Security initiative."

Still, Hagel said even with those additional funds, the U.S. military force will be too small to fully carry out the administration’s defense strategy.

In a cost-saving measure likely to meet opposition from Congress, Hagel said the Pentagon plans a new round of base closures. Congress has fought in the past against the closures as a way of protecting jobs in home states.

The force cuts were based on an assumption that the military will no longer be set up to conduct long and large operations, like those in Iraq and Afghanistan, Hagel said.

Technology also will be emphasized to allow the U.S. military to maintain an edge over enemies, and U.S. forces must be structured to "respond quickly to all contingencies and decisively defeat any opponent should deterrence fail," he said.

"Accordingly, our recommendations favor a smaller and more capable force, putting a premium on rapidly deployable, self-sustaining platforms that can defeat more technologically advanced adversaries," Hagel said.

For strategic nuclear forces, Hagel said the Pentagon would keep the three-pronged force of land-based missiles, missile-firing submarines and strategic bombers.

Special operations commando forces will increase from 66,000 to 69,700.

Gen. Martin Dempsey, chairman of the Joint Chiefs of Staff, said the budget proposal "represents both sound national security and fiscal responsibility."

American Enterprise Institute scholar Mackenzie Eaglen said the latest defense cuts will continue to weaken the U.S. military and its technological edge.

"President Obama is submitting another defense budget that essentially seeks to cash in a peace dividend in a world with little peace," she said. "His own director of national intelligence recently told Congress that in over a half century, he has not experienced a time when the U.S. has ‘been beset by more crises and threats around the globe.’"

Retired Air Force Lt. Gen. Thomas G. McInerney, said of the proposed cuts that they are "continuing on its path of unilateral disarmament that was started by Defense Secretary Robert Gates in April 2009."

"This action announced today will escalate the demise of our military unilaterally and we still have no strategy for defeating radical Islam after 9/11. This is very dangerous," he said.