MONTGOMERY, Alabama - A review of defense programs produced every four years could bring big changes in the Pentagon's fiscal 2011 budget, beyond the sweeping overhaul already unveiled for 2010, U.S. Defense Secretary Robert Gates said on Wednesday.

We have to be prepared for the wars we are most likely to fight -- not just the wars we're best suited to fight, or threats we conjure up from potential adversaries with unlimited time and resources, Gates told officers at the Air War College at Maxwell Air Force Base in Montgomery, Alabama.

The government's fiscal 2010 year begins on October 1.

Gates said he had put off decisions on several weapons programs until the Pentagon completes its Quadrennial Defense Review (QDR) later this year. Those programs include amphibious military operations, a next-generation cruiser and work on a new bomber.

The review will let the Pentagon fully incorporate lessons from the wars in Iraq and Afghanistan, and other rapidly evolving threats, for future weapons. War in the future will be often be a hybrid blend of tactics, he said.

As part of the quadrennial defense review, Gates said the Air Force faced critical questions about the requirements for a new manned bomber and the implications that growing use of unmanned aerial systems has for the manned fighter fleet.

For example, the Reaper unmanned system built by Northrop Grumman Corp has a range of 3,000 miles, far more than the Pentagon's manned F-16 fighters, and can be loaded up with many weapons, he said.

Decisions on a new manned bomber, which the Air Force had hoped to have in service by 2018, would also be affected by the outcome of new arms control negotiations between the United States and Russia, Gates said.

Another question, he said, was how many aerial refueling tankers the Air Force would ultimately need, given that unmanned aerial vehicles -- which were an increasingly important part of the fleet -- do not refuel in mid-air.

As we look toward the future, I have directed the QDR team to be realistic about the scenarios where direct U.S. military action would be required, he said.

The Pentagon also remains focused too much on buying weapons for individual services that are so costly and complex that they take forever to build and only then in very limited quantities, Gates said. That is why any new competition to build combat search-and-rescue helicopters will be a joint program, rather than the now-scrapped Air Force competition, he said.

Gates defended his recent decisions to halt production of the Lockheed Martin Corp's F-22 fighter at 187 fighters, and to increase funding for the F-35 fighter, also being developed by Lockheed, from $6.8 billion to $11.2 billion. Russia, he noted, was six years away from fielding a new fifth-generation fighter while China still needed 10 to 12 more years.

Looking forward, the goal of our weapons buying is to develop a portfolio -- a mixture of weapons whose flexibility allows us to respond to a spectrum of contingencies, he said. Focusing exclusively, or obsessively, on a single weapons system designed to do a specific job or confront a single adversary ignores what a truly joint force can and must do in the 21st century.

Gates acknowledged that he faced some resistance in Congress for his plan for a sweeping overhaul of weapons spending, but said he hoped to leverage acquisition horror stories from years past to get support from lawmakers.

Gates said he was laying my body in the tracks to oppose moves by lawmakers to split the purchase of new Air Force aerial refueling tankers between Boeing Co and Northrop Grumman.

Meanwhile, Gates said his continued support for the Littoral Combat Ship being developed by Lockheed and General Dynamics Corp was based on its versatility and ability to go places too dangerous for the Navy's larger vessels.

As we saw last week, you don't necessarily need a billion-dollar ship to chase down a bunch of pirates, Gates said.