WASHINGTON — The growth of federal spending on health care will continue to decline as a proportion of the overall economy in the coming decades, in part because of cost controls mandated by President Obama’s health care law, the nonpartisan Congressional Budget Office said on Tuesday.

The budget office said in its annual 25-year forecast that federal spending on major health care programs would amount to 8 percent of gross domestic product by 2039, one-tenth of a percentage point lower than its previous projection.

With the latest revision, the budget office has now reduced its 10-year estimate for spending by Medicare, Medicaid and other health programs by $1.23 trillion starting in 2010, the year the health care law took effect. By 2039, the savings would amount to $250 billion a year today, or about 1.5 percent of the economy.

Many factors contributed to the change, including lower anticipated economic growth and a downward projection for interest rates over time. But another factor was a finding that the federal government might be able to sustain a low growth rate of payments to providers in line with requirements set by the health care law.