WASHINGTON — One of the key elements of President Bush’s State of the Union address tonight, his proposal to cap tax deductions for health insurance, will have an extra bite in the New York City area because of the high cost of health care and insurance in the region, researchers said.

“It’s going to hit high-cost areas like New York much harder,” a spokesman for the Kaiser Family Foundation, Larry Levitt, said.

“You can kind of guess if you have higher premiums, it’s going to affect you more,” a project manager for the federal Agency for Healthcare Research and Quality, John Sommers, said. “Whenever you have something that affects people with higher costs … New York and the Northeast gets it.”

Mr. Bush is proposing limiting the tax deduction for employer-based health insurance plans that cost more than $15,000 a year for a family or $7,500 a year for an individual. In 2004, the New York metro area had the highest health care premiums in the country, according to a federal survey. The average premium for family coverage was $11,244. Figuring in inflation, that figure rose to about $12, 875 last year. By 2009, when Mr. Bush’s plan would take effect, the average family cost in New York could be close to the $15,000 cap, meaning that a substantial number of New Yorkers would find themselves being taxed on at least a portion of their health insurance.

A fact sheet released by the White House says about 20% of Americans with health insurance could find themselves paying higher taxes because of the cap, though officials said some employees might seek cheaper plans to avoid that possibility.

Mr. Sommers said the survey data gathered by his agency do not permit reliable state-by-state or locality-by-locality estimates of the impact of Mr. Bush’s proposal.

A disproportionate impact on New York and other high-cost states could pose political problems for the president’s health plan. In the past, high-cost states have banded together to defeat proposals they saw as unfair, such as efforts to strip the federal deduction for state and local tax payments.

Mr. Sommers said upstate New York would probably see less impact from the changes proposed by Mr. Bush because health costs there tend to be closer to the national average. Some suburban New York areas could see even more impact than the city itself. “Connecticut is about as bad as it gets” in terms of statewide costs, he said.

The proposed deduction cap is part of a plan to give all those who purchase insurance a new exemption from federal income taxes. The exemption would be $7,500 for an individual and $15,000 for a family, regardless of their expenditure on insurance.

The White House said the new deduction should encourage the uninsured to buy insurance. A decrease in the rolls of uninsured could be a boon to states and localities with large numbers of those without insurance. White House officials say the plan is revenue neutral, meaning that it will not result in a net tax increase.

Mr. Levitt said the new deduction would be most beneficial to those already purchasing insurance and to wealthy individuals living in low-cost areas. He said he doubts the number of uninsured in high-cost areas would change much under Mr. Bush’s plan because those of modest means get little benefit from a tax deduction and higher premiums make basic coverage unaffordable for many. “Almost half of the uninsured have zero federal income tax liability. Most of the rest are in the 15% bracket where a deduction doesn’t mean much,” Mr. Levitt said. “It won’t provide as much of a subsidy where costs are higher.”