WASHINGTON — With Congress increasingly unable to resolve budget disputes, federal programs on automatic pilot are consuming ever larger amounts of government resources. The trend helps older Americans, who receive the bulk of Social Security and Medicare benefits, at the expense of younger people.

This generational shift draws modest public debate. But it alarms some policy advocates, who say the United States is reducing vital investments in the future.

Because Democrats and Republicans can't reach a grand bargain on deficit spending — with mutually accepted spending cuts and revenue hikes — Social Security, Medicare and Medicaid keep growing, largely untouched. Steady expansions of these nondiscretionary "entitlement" programs require no congressional action, so they flourish in times of gridlock.