WASHINGTON — President Obama said yesterday that the Internal Revenue Service would start making it easier for companies to automatically enroll workers in retirement plans, and that his administration would help individuals convert their tax refunds and unused vacation pay into savings.

In his weekly radio address, Obama said the recession had threatened retirement security for millions of older Americans, who have seen the values of their homes and 401(k) plans plummet.

"Half of America's work force doesn't have access to a retirement plan at work, and fewer than 10 percent of those without workplace retirement plans have one of their own," Obama said. "We cannot continue on this course."

The president announced immediate changes in government practice, and pledged to work for legislative changes that would require companies to automatically enroll workers in retirement savings plans.

One change will streamline the process for automatic enrollment in 401(k) plans. At present, employers usually seek IRS approval of changes in their plans to make sure they are complying with the law.

By issuing pre-approval, the IRS will make it easier for plan sponsors to adopt automatic enrollment plans more quickly, and to increase the rate of individual contributions, even without case-by-case approval by bureaucrats.

The government will give similar help to employers looking to enroll workers in simple individual retirement accounts, as long as the employees are free to opt out.

Another change will allow people who get tax refunds — more than 100 million families, by one estimate — to direct the IRS to directly deposit them into a savings plan.

As early as 2010, people will be able to buy U.S. savings bonds with their tax refunds just by checking a box on their tax forms. A few weeks later, the bonds will show up in the mail.

Treasury and IRS officials also will let employees contribute their pay for unused vacation time to their 401(k) plans.

Down the road, Obama said, he would press Congress for legislation to enroll workers without workplace retirement plans in IRAs through payroll deposit contributions at their jobs.

Aides to the president said the proposals were part of Obama's long-term economic strategy.