WASHINGTON — President Bush can balance the budget within five years, or he can get Congress to extend his tax cuts beyond their scheduled expiration, the Congressional Budget Office reported yesterday — but probably not both.

Bush has said otherwise, committing himself in Tuesday's State of the Union address to providing Congress on Feb. 5 with spending and tax proposals that would balance the budget by 2012.

"We must balance the federal budget," Bush said. "We can do so without raising taxes."

But the nonpartisan CBO, in its annual report on where current spending and tax policies would take the budget over the next 10 years, painted a picture of a budget that needed an extra infusion of cash or a sharp reduction in outlays if revenues were to exceed spending.

And even if the budget could be balanced in 2012, said Peter Orszag, the CBO's director, the retirement of the baby-boom generation could quickly unbalance it: Not only would the wave of retirees force the government to spend more for Social Security, Medicare and other benefit programs, he said, but it would drain the population of taxpaying wage-earners.

Senate Budget Committee chairman Kent Conrad of North Dakota, a Democrat, noted that the CBO is required by law to base its projections on current spending and tax law, without regard to likely changes. The Iraq war, he said, is underfunded — the administration is expected soon to ask for another $100 billion for this year — and the tax cuts that Bush wants made permanent are due to expire at the end of 2010.

Brian M. Riedl, budget specialist at the right-of-center Heritage Foundation, said the new numbers implied that balancing the budget by 2012 without increasing taxes meant that federal spending could be $294 billion greater in 2012 than 2007.

But in that period, he noted, Social Security, Medicare and Medicaid costs would rise by $367 billion.

Under current law, if the tax cuts expire as scheduled at the end of 2010, the budget would swing nearly to balance in 2011 and show a $170 billion surplus in 2012, according to CBO estimates.

But that would occur only if Congress allows the tax cuts to expire. Such a decision — far from a forgone conclusion — would generate $268 billion in revenue in 2012.

Without it, there would be a $100 billion deficit.

The budget office said other likely tax actions — notably, continued relief from the alternative minimum tax, which increasingly hits middle-class taxpayers instead of the wealthy — would add $160 billion more to the 2012 deficit.

On the spending side, big troop reductions in Iraq could save $43 billion in 2012. But that could be more than offset if Congress lets domestic appropriations, which Bush has targeted for no increase even for inflation, grow as fast as the combination of economic output and inflation.

Altogether, the policy changes identified by the CBO could turn the 2012 surplus of $170 billion into a deficit of $245 billion.